We didn't have much time to react, but MARVEL VS. CAPCOM 2 has been available on Pandaapp now. It can be played both on iPhone and iPad. So far it looks very nice, if you can handle the virtual controls, you'll be in for a good time.
Although the app description says it will not work with iPhone 3GS, but according to the report of Toucharcade, some 3GS users have tried it, just something slowdown, else would be OK.Description
Wolverine & Spider-man VS. Ryu & Chun-Li ! One of the most popular arcade-fighting games of all time arrives on the App Store for your iOS tablet or mobile device! Marvel vs. Capcom 2 brings together legendary characters from the Marvel and Capcom franchises to duke it out in an insane, action-packed, tag-team fighting experience. From Ryu to Wolverine, pit your favorite heroes in dream match-ups thanks to the robust 56-character roster. With the optimized iOS touchscreen controls, 2-player versus-mode, unlockable secrets and characters, you better buckle up and prepare to be taken for a ride!
・A full-featured port of one of the best fighting games of all-time
・Marvel vs. Capcom 2 has previously only been enjoyed in arcades and consoles for over a decade. Now enjoyable anywhere, anytime with the iOS version.
・Deep 56 Character Roster Featuring Characters from the Marvel and Capcom franchises
・One of the largest character rosters in any fighting game to date
・Bringing together Marvel’s greatest comic-book heroes and Capcom’s fiercest video-game fighters
・Versus Mode Battles
・Users can connect with other iPhone users via Bluetooth and play against each other
・New streamlined touchscreen controls optimized for iOS
・Introducing the “Flick Button,” a new control feature that streamlines complex inputs
The game can be played on any version after iOS 5.0, on iPhone 4, 4S / iPod touch 4th generation/ iPad 2, iPad 3rd generation. Note: This application will not work on the iPhone 3GS, iPod Touch 3rd generation or earlier, nor the iPad 1st generation.