It takes a certain genius in crafting a great video game narrative. You have to account for player agency, pacing, stylistic decisions that bring in narrative focus that could take away gameplay options, and ensure that your protagonist is (in some form or another) proactive enough to avoid the (often times misused) accusation of the story "simply being a movie." Of course, a developer could more evenly separate story segments and gameplay more frequently to alleviate problems, and I have no problem with that. However, increasingly with the industry, we're seeing a trend where stories involving the gameplay intertwine with one another; a trend where gameplay comments on story and vice-versa, and that, in my opinion, is some variation that I adore when done well.
There have been examples of video game narrative or gameplay subversion (like with Super Mario Bros 3 all being a play or how it's impossible to beat Vile the first time around in Mega Man X), although not quite as much as when we get into the sixth generation of video game consoles, and never quite as up-front. Games in the seventh generation-onward, such as BioShock, Spec Ops: The Line, Dark Souls, Splinter Cell: Blacklist, or Brothers: A Tale of Two Sons frequently employ content to upset the established order of what players come to expect that delves into the mechanics to create a deeper impact on the player on the gameplay, the syuzhet and fabula construction, or both. Halo 2 and Metal Gear Solid 2: Sons of Liberty subversions are of different caliber, however, since they come into play as both huge blockbuster sequels to original games as well as swap-out the much loved and recognized main character and introduce someone new in the storyline. While there are a LOT of other topics to discuss, the addition of a secondary protagonist and their changes on the game itself will be the main focus on this article. *WARNING: this article features plot spoilers for Metal Gear Solid 2, 3, V, and Halo 2 and 4*
At the marketing stage of each game, everyone thought their fan-favorite protagonist would be the center of attention. We had Snake sneaking around terrorists and Master Chief defending Earth from Covenant baddies. There was no warning or noticeable indication that Raiden or the Arbiter would take center stage (or at the very least share it). While Halo 2's marketing could be excused as a case of 'creatively truthful' advertisement (as the Earth levels of Halo 2 ARE all Master Chief centered), Sons of Liberty outright swapped Raiden out for Snake in preview videos. For Halo 2, the only indication we would be getting the Arbiter at all was the reveal that Elites would also be featured in the multiplayer.
The beginning sections of both Halo 2 and Sons of Liberty felt like a comfy pair of slippers. Snake infiltrating a secret location to discover a new Metal Gear with Ocelot thrown in the mix? Hell yes. Master Chief laying down fire as the Covenant slowly erodes humanity's defenses? Oh, you know me so well. Only, at the end of each respective segments of story, we begin to see certain changes in the story. Things that we don't expect to happen. Snake FAILS at stopping Metal Gear Ray and it's uncertain whether he actually survives the encounter (although his narration at the beginning reveals that this is a memory from two years ago), and the Covenant RETREAT from Earth and (even more surprisingly) the fleet they bring isn't the usual overwhelming flood of death they're known to bring. Something feels very off for both cases. In the case of Halo 2's opening cutscene, we're split between the Master Chief receiving a medal of valor and the Arbiter receiving public torture and humiliation. Why did they bring this weird Elite into the story? Is he the new bad guy? What about Snake? Maybe the story is setting up seeds that will bear fruit years later with Snake spending his time preparing for the next infiltration.
Then, we bring in the new guys. We see here a huge divergence between how each developer handles its new protagonist. The Arbiter seeks redemption in the eyes of his religion, believing that his new-suicidal task is a glorious chance to clean his name and reputation. On the other hand, we have Raiden, a new Foxhound operative infiltrating Big Shell and save hostages from a terrorist group claiming that their leader is Solid Snake. Oooooo, drama.
Both games have a big tendency to rely on player memory of the previous game. Sons of Liberty (hereby referred to as MGS2) begins as close to the first Metal Gear Solid game (referred to now on as MGS1) without just remaking it with a new engine. While other splendid writers have gone over the minutia of similarities between MGS1 and MGS2 (read here for a great break-down), the main thrust of the argument is how strikingly similar it is to the general beginning of the game first "Solid" game - Raiden infiltrates the compound with limited equipment while Colonial Campbell provides insight and instructions for him, all the while asking about Solid Snake and hoping to live up to the legend (like the players most likely would be). While his abilities are more acrobatic than Snake's, Raiden has roughly the same physical capabilities as Snake. He's likewise tasked with stopping terrorists, while encountering a bevy of side-characters who flesh out the story, themes, and begin to unravel a larger conspiracy going on behind the scenes (once again, VERY much like MGS1).
However, by the end of the third act, we come to a grinding halt as we uncover the Patriots, Jack's past, and learn about how Solid Snake actually fits into the entirety of the puzzle. The game suddenly becomes a critical analysis of itself in dealing with player objectives and the players' desire to be empowered, thinking themselves to be like the legendary Solid Snake. The player even comes to a crossroads of either completing their mission instructed by the twisted Patriots, which would also save a young baby, or die and allow Solidus (the main enemy of the game, though still manipulated big bad) to kill you and go after the Patriots and free the world. In order to advance to a win state, you have to kill Soldius. Raiden tosses away his dog tags and comes to the conclusion that he wants to find his own way in life where he isn't following anyone's beliefs, but his own. In a very anti-climactic ending, Jack reunites with his girlfriend contemplating their lives with their future child with Solid Snake chasing after Ocelot, the biggest story thread we, as players, were teased with, yet never given.
The new protagonist not only gives the audience an eye for reexamining the plot in a new light, with interesting new avenues of storytelling, but, in the case of MGS2, we now reexamine how the mythos and expectations of the first MGS1 game actually dictate the progression of the narrative. The gameplay and the story surround the idea of you are following Solid Snake, both figuratively as Raiden follows in Snake's footsteps through VR training, seeing the aftermath of his actions, and getting involved with the story threads that Snake started in the previous game and continued in MGS2, as well as metaphorically game-wise as MGS2 follows in the established footsteps of MGS1's design, beginning narrative structure, and archetypes. Raiden's inclusion in the game reinforces the idea, through gameplay and narrative entwined, of manipulation based on expectations and deconstructs the very series it embraces.
The Arbiter in Halo 2 is, literally and figuratively, another story. After the Chief's Earth excursions, The Arbiter embraces his title for the sake of religious redemption and opens up a side of the Covenant we've never seen before - where the story treats them as "people." While getting his troops amped up for battle with a heretic force, Half-Jaw remarks that while the lives of his troops matter to him, the Arbiter's does not, with The Arbiter agreeing full-heartedly earning a reaction of curiosity from Half-Jaw. In an attempt to kill a heretic to their religion, Arbiter plans on destroying the station their on with him sacrificing himself - the Elites honoring him with praise as they make their way out. After he is saved, the Prophets confer with him the aggravating nature of the Elite's political stances. Moreso than the humans, we have a deeper understanding of the Covenant's inner workings as a society rather than just the "front-line soldier" excursions Halo: Combat Evolved had showcased. Even by the fact that the Arbiter is tasked with killing members of the Covenant who have turned heretical brings about far more complexity to the equation as the enemies (though the same by gameplay standards with Heretic Elites and Grunts) are refashioned into a splinter faction based on ideological differences.
While Master Chief is doing the same types of story errands on one side of the narrative (namely, exploring Forerunner ruins and Covenant ships, blowing things up, leading troops into battle), the Arbiter does FAR more heavy lifting in the narrative with his disillusionment with the Covenant and eventually his own religious beliefs. The Covenant civil war that springs up in the third act actually effects The Arbiter in a more fascinating way than the Chief, who the game gives the task of killing every living creature that isn't a homosapien. The Covenant is split in two and the player finding allies among some of the Covenant species you've been siding with, while gunning against the others you fought shoulder-to-shoulder with on previous missions. It's impact moment seeing how quickly allegiances could have turned for the sake of religious fervor. The Arbiter's gameplay is almost identical to Chief's in every way, save for the starting weapons for The Arbiter's levels (usually Covenant-based) and his ability to camouflage. Rather than take the narrative structure and try to comment on the gameplay (like in the case of MGS2), the gameplay remains a fixed point for both protagonists, but in doing so places the focus on how differently each hero's story unfolds and the differing experiences between them.
For both games' sequels, the narrative/gameplay dissonance (or rather, "re-focusing") was abandoned for simplicity, though this is not a condemnation of not attempting experimentation. Halo 3 removed the gameplay effects of the Covenant civil war to the point of only the Elites being your visual allies in the cutscenes and gameplay, with The Arbiter unfortunately taking a backseat to the Chief - and the only way to play as him was in co-op. Metal Gear Solid 3: Snake Eater was a far more simple tale filled with gameplay and narrative that mostly worked in-sync with each other, rather than trying to make the player aware of the artifice of the medium. Perhaps these changes were brought along by audiences negative reactions to new protagonist, or perhaps it was caused by player feedback feeling as though the game muddled the waters of understanding gameplay standards, or maybe it was because the developers believed the players would already be weary of that type of trick and decided to refocus their energies elsewhere. I can only speculate. In any case, changes were made for the sequels where the tried-and-true faces for the franchise (or a very similar face and voice, in the case of Metal Gear Solid 3: Snake Eater) were brought back to the forefront.
As of right now, both the Metal Gear Solid and Halo franchises' most recent games (Metal Gear Solid V and Halo 4) have found great balances between narrative experimentation without denying players' their sense of accomplishment through gameplay with the most recognized faces of the franchise taking center stage.
Both MGS2 and Halo 2 utilize secondary protagonists not only for increasing narrative scope, but also to affect player interactivity. Whether it's causing the player to pause at their own actions, shift their own sense of objectives and levels of sympathy, or even cause them to reexamine the predecessor's original design, these new protagonists ensured that, in one form or another, players are forced to adjust to a new status-quo in contrast to the series previously established blueprint. And without these introductory steps to post-modern and subversive games, the video game landscape, I feel, would be a very different place for the industry, let-alone for games pushing the boundaries between interaction and narrative.