You should have no real issue playing marvel vs capcom, I have personally never used the mame emulation on psp but I have heard that it runs cps2 emulation alrite. You should, by that token, also be able to run marvel super heroes vs street fighter and xmen vs street fighter (I believe these are also psx games, but I hear that the arcade versions are better)
Marvel vs Capcom 2 was not released as a cps2 game or cps3 for that matter. Therefore I highly doubt its emulation through mame. The version of it for PS2, xbox, gamecube etc is obviously unobtainable aswell on psp.