« E3: NEW MARVEL VS CAPCOM 3 GAMEPLAY FOOTAGE »
Here it is -- the first real in-depth look at Marvel vs Capcom 3 gameplay! I am pretty much speechless at this point -- the game looks amazing!
Roster content isn't the only thing that's not yet finalized. While it's all but certain the button configuration will mimic Marvel vs. Capcom 2's four attacks and two assist buttons, the default layout of the buttons is still in question. Presently, the three main attacks in Marvel 3--light, medium and hard--line up on the top row of an arcade stick, where the LP, HP and A1 buttons call home in Marvel 2. The bottom three buttons default to the launcher attack and the two assist buttons (LK, HK and A2 in MvC2). Punch and kick attacks are no longer explicitly separated, though the familiar shortcut for dashing--both punch buttons pressed together--can still be executed with a simple press of the light and medium attacks. It'll take time to adjust to the new button layout, but it's nothing a few hours of training mode won't solve. And if you're an avid Marvel nerd like me, you know a few hours of training mode ain't no thang when the game releases sometime in the uncertain future. It's Marvel, baby.
Source: IGN

Here are a few more gameplay videos from E3!
Source: SRK

Videos of Morrigan and Felicia in action! Thanks to EventHubs fro uploading these. I think they originally came from Famitsu.
Character select screen.