Although Marvel Comics has been around since 1939, its characters didn't really penetrate the mainstream until the last 15 years or so. While the general public knew of DC villains like The Joker and Lex Luthor, the same probably couldn't be said for the likes of Thanos or Galactus. However, with the Marvel Cinematic Universe being the most popular film franchise in the world right now, Marvel's villains are starting to become a little more well known.
Now, the mainstream public are aware of countless Marvel heroes and villains, ranging from household names like Iron Man and Captain America, to even the most obscure characters like Black Knight and Starfox. With Marvel being so successful at the moment, it's only a matter of time before the gaming world starts to pump out Marvel game after Marvel game. Thankfully, there's plenty of inspiration to draw from, and there are plenty of Marvel villains that could feature in great video game experiences.
Loki
One of the most popular "villains" of the MCU, Loki would be the perfect fit for a stealth action game. As the young trickster god, players could sneak through Odin's palace hallways, hiding behind ornate pillars and pranking Asgardian soldiers. As the story progresses, and Loki gets older, the stealth gameplay could evolve alongside the character and narrative, granting Loki more powers and abilities relating to his illusion magic.
A potential Loki game could take some inspiration from the dormant Thief series, using its first-person stealth gameplay as a basis for Loki's own particular brand of sneaking. The theoretical game could also look to Arkane's titles, namely Dishonored and Deathloop, and their range of magic abilities. For instance, Deathloop's "Shift" ability would fit a Loki game perfectly, giving the player the ability to dart around the map with magic. Loki could also use his illusion powers to make doubles of himself, or use his powers to make himself temporarily invisible.
Ego The Living Planet
While he was only briefly seen in full planet form in Guardians of the Galaxy Vol. 2, Ego would actually make for a pretty great park-builder/sim game. Players could control Ego, using his celestial powers to grow life and ensure that his planet reaches perfection. Once the planet has been cultivated enough, the player could then try to spread their planet's life to the rest of the galaxy, turning the game from a Sims or Planet Coaster-like experience into more of a 4X strategy game.
Green Goblin
While fans of Spider-Man have gotten to play as wall-crawler countless times, and have even gotten the chance to leap around Manhattan as Venom, there have only been one or two instances where players could actually control Spidey's nemesis, Green Goblin. A Green Goblin game probably wouldn't offer any revolutionary gameplay, but its traversal mechanics could be pretty unique, with Goblin's iconic glider being the basis of the character's in-game movement.
Green Goblin's host of pumpkin-related gadgets and weapons would surely make for some varied combat sequences, and the game could put the focus on aerial combat, controlling more like an Ace Combat game than Marvel's Spider-Man. Narratively, the game could put the focus on Norman/Harry's dissociation from their actions, with the Goblin serum causing memory loss, possibly tying into some subversive gameplay elements.
Taskmaster
Taskmaster may not have had the best cinematic debut in Black Widow, but the character is still beloved among many fans, and for good reason. Taskmaster's primary ability, photographic reflexes, allows them to memorize and imitate the fighting styles of anyone they come across, which could make for one incredibly varied video game.
With inspiration from games like Mortal Shell and Nobody Saves the World, Taskmaster could act like a blank slate character who only has a basic set of skills and moves. The player would then unlock new forms throughout the game, unlocking the ability to fight like the heroes they're facing off against. By the end of the game, the player would be able to switch between all the Avengers' different fighting styles, chaining combos together using a variety of Hawkeye, Black Widow, and Spider-Man's moves, for example.
Magneto
A game that could take Watch Dogs' initial promise of "you can hack everything," and actually deliver on that concept, a Magneto game in which players could manipulate every aspect of their surroundings would be unbelievably unique. On the surface, the game could have fairly simple third-person action mechanics, with standard Magneto abilities like pushing and pulling enemies, and throwing objects around the environment.
On a deeper level, a Magneto game could give players control over every single object that contains metal. While some objects could be used simply as throwable weapons, using similar mechanics to something like Star Wars: Force Unleashed, some metallic objects could be used in more inventive ways, like what can be seen in the "too much iron in your blood" scene from X-Men 2.
Winter Soldier
A potential Winter Soldier game set during the Cold War could be pretty compelling. Using gameplay heavily inspired by the Hitman series, a Winter Soldier game could task players with executing a range of Hydra assassinations, all on various S.H.I.E.L.D. members or some of Marvel's lesser known, older heroes. Players could use either stealth or brute force during missions, with the Winter Soldier's proficiency with snipers making him the perfect long-range silent killer and his heavy metallic arm making him just as effective at close range.
Thanos
Marvel did an excellent job at making the Infinity Stones look absolutely devastating during Infinity War and Endgame, but they also looked really fun to use. While a few games have tried it over the last few years, like Fortnite and even God of War, the full potential of a Thanos game in which he wields the Infinity Gauntlet has not yet been realized.
The game would have an immediate narrative and gameplay hook that sees Thanos needing to find the Infinity Stones. It's simple, but it's effective, and it is all the motivation a player needs to seek out the largest power in the galaxy. As players progress through a potential game, the more Infinity Stones they find, the more powerful they could become, granting powerful purple lasers, time-bending abilities, and powers that can change the fabric of reality.
Galactus
Probably an MCU big bad later down the line, Galactus is a giant, world-eating entity that often can't really be stopped, just tricked and pushed away for a bit. He may not be able to provide a game full of intricate mechanics, but a Katamari-type of game might be pretty fun, especially if a tongue-in-cheek tone is used.
Marvel fans could go from planet to planet, consuming each one and growing increasingly bigger until entire galaxies can be eaten. To spice up the gameplay a little, the player could come into contact with various Marvel heroes as they try to stop Galactus from eating the universe.