From what I've heard, but I haven't played it to confirm this, Tatsunuko VS Capcom features some rather annoying things when it comes to games in the Capcom VS series. One button Ultras is one of these features. Also, if the only play is improved 100% over SSBB on the Wii, it is still severly lacking.
Do take in mind though, that the style of each game is drastically different. SFIV and I imagine SSFIV are less focused on being ultra fast paced, insane chain combo, high octane fighters and more about strategy, defense and skill. Don't get me wrong, I think MvC2 takes skill to be great at, but with how easy it is to pick Megaman, Iceman, Cable and spam assist and Megaman blast, it isn't hard to against above average players.