When I got into Street Fighter again two years ago after like a 15 year hiatus, I relearned the painful truth: if you wanna get good (say, competitive against people who consider fighters their favorite genre), you gotta put a LOT of time in. Practice practice practice. All there is to it.
Starting with a cheap and easy team would probably help. Speaking as someone who blows at MvC3, it seems like Wesker, Sentinel, and Hulk are cheese.
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Yoblazer: http://oi52.tinypic.com/ad21i1.jpg
Watch and you'll see... someday I'll be... part of your world!