The fighting genre has become a widely respected genre in the video game community. Although fighting games were at a slump in the 21st century (mostly due to ripoffs of initially successful franchises as well as just plain poorly made yet mildly successful games such as Mortal Kombat), fighting games are back thanks to Street Fighter IV. Now that most series being released nowadays are highly praised, will fighting games hit a slump again?
To avoid such a drought in the genre (seriously, I don't want another era where the only fighting games are a single Capcom crossover that's competitively ruined by a glitch and a plethora of bad, annual Mortal Kombats), the genre will need further improvement sometime soon.
I think Skullgirls and Ultimate Marvel Vs. Capcom 3, from a gameplay standpoint, took the genre further. Skullgirls uses the Capcom vs. SNK 2 ratio system, allowing a player to choose from a team of 3 normal characters, a team of 2 slightly stronger characters or a single powerful character. Teams have the option to use assist attacks as well as Delayed super moves whereas single characters are just plain powerful. Skullgirls is great because the type of battle will truly vary despite only having 8 characters; battles involving teams will only be one round whereas 1 on 1 battles are round-based. The small amount of 8 characters is truly diverse; Ms. Fortune has a head that can fight independently while her headless body is controlled normally, Parasoul and Peacock have insane keepaway (shoutouts to StarGalaxy's saltiness), Cerebella is a huge heavy hitter a la Hulk, etc. With Skullgirls' variety of battles and characters, each match will feel different quite a bit than the other. I feel this is what fighting games need: varying battle experience. I believe Tekken Tag Tournament 2 is doing this as well by letting someone choose between 1 character or a tag team of 2. Character variety is one thing, but fighting against a multitude of different kinds of teams is a plus. It changes strategy and thus makes the game more interesting.
Tatsunoko Vs. Capcom had two mecha characters, Gold Lightan and PTX-40A; these characters were insanely huge compared to the other characters. They had their own features while lacking the features of a tag team; they couldn't do air combos or team hyper combos and couldn't have a partner. However, they had much more health and did tremendous damage. I think they had super armor as well.
Why not combine an extended team ratio system like Skullgirls' and giant mecha characters like TvC's with the extensive character variety that Skullgirl's and UMVC3 has? The possibilities are crazy; there's a single regular character fighting a single mecha, or a team of 3 fighting a team of 2. I think fighting games need to explore different ways to make each battle fresh and different than one another; most other fighting games only have one factor that make a match different than another and that's whether one is fighting a rushdown or a projectile-heavy character. Battles need more variety since variety induces deeper strategy and thus a truly long living fighting game.
EDIT: I do think Street Fighter X Tekken's Gem system contributes to this as well. Not only do I feel personal customization is great and helps a player connect to the game more tightly, but it also changes circumstances as well. I think there's a new gem that extends that amount of time Pandora Mode is active, which is something to fear if used properly. I would say UMVC3's X-Factor also changes strategy a bit but it doesn't add variety to the game since it's always available. It's merely just a boost.