No mention of the 4 gods of MvC2.
Sentinel
One of the heaviest, hardest hitting characters in the game, turned into its fastest character thanks to exploits (fly/unfly, fast fly).
Storm
Best runaway in the game thanks to air control. In MvC2, whoever has the higher ground in the air usually wins, air control means she can delay her fall and, even fly off the top corner of the screen and stay there to build meter. Additionally, she's also a great overall character, good movement thanks to 8 way airdash, damage, etc. means that she's great at both keepaway and rushdown.
Magneto
Very good movement, thanks again to 8 way airdash. Combined with a good assist (Psylocke) can continue to reset an opponent into death. You know the term "vortex"? The very genesis of that term came from Arturo's description of Yipes Magneto/Storm/Psylocke play - once he got you in the combo, he'd suck you back into the vortex. Magnus didn't even need to knock down, he could vortex you from nearly any position.
Cable
Probably the only character purposely designed to be top tier. Biggest advantage is AHVB (air hyper viper beam), by tiger kneeing his air hyper viper beam, you could perform it close to the ground and continue to combo it into itself. With 5 bars (pretty easy to come by) , Cable could kill a character off any single mistake from full screen.
The other thing to note is that these characters tended to have good synergy with each other. Most top tier teams e.g. MSP, Santhrax, Matrix (JWong's team), etc. had at least 2 gods plus 1 high tier.
But the real best team in the game, the one that by all rights should dominate other teams if not for the sheer execution requirement, surprisingly uses only 1 god tier - Strider/Doom/Sentinel aka Clockw0rk.
Run by SoCal legend Clockw0rk, the team specialized in one thing - lockdown. Once Strider popped orbs, the team could keep a character perpetually locked down in blockstun. This was the classic Mahvell trap - if you get caught and you just block, you die from chip, if you press any buttons, you eat a combo and die.
The only reason you don't see Strider/Doom more dominant is the fact that it takes absolute perfect play to pull it off, and only one player so far has been known to be able to do this - Clockw0rk.
Street Fighter 4
Cammy
Hahaha, you think this is a game? Imagine a Cammy that could do cannon spikes with no air restriction just like the ones she does when using meter, now imagine she jumping you to apply pressure and the easiest stun in the game.
Finally, someone else who realizes how much Cammy could have run the game if we stuck to Vanilla.
