I liked Super Street Fighter 2 and Alpha 3. They had my two favorite characters in the series, Vega and Cammy. I used to be pretty good with them back in the day. I could beat most of the usual Ryu/Ken people out there with them, and it was cool because they didn't seem to expect much out of Vega or Cammy.

Wasn't all the Alpha series pretty much the same game, only some different characters?

I've only played the original (Street Fighter) on MAME, and its terrible. Considering that I think Street Fighter was an relatively obscure arcade game, and not a very good one, its suprising that they ever made a sequel to it. Good thing, though, because the series after that was the best.