I don't believe anyone's mentioned it yet in this thread, but I'd like to give a special mention to Capcom Classics Collection Reloaded for PSP. It contains excellent ports of SF2, SF2 Champion Edition, and SF2 Hyper Fighting (along with many other great early Capcom games).
I believe they're actually ported from the PS1 versions, so they're not quite arcade perfect, but they are very close. (Score display at the top of the screen is the most noticeable difference.) You can choose the original CPS1 music or the "arranged" soundtrack (the soundtrack introduced with the 3DO version of SSF2T). You can also choose three different displays: 1:1 pixels with no scaling (black border on all four sides), full screen stretched to all borders, or 4:3 full screen (which stretches vertically to the PSP top and bottom borders, but actually condenses slightly horizontally due to the original image being not actually 4:3 ratio).
The game is compatible with PS Vita and PSTV, and is a real joy to play on both of those systems. It looks beautiful on the Vita's crisp display with vibrant colors, and the PSTV lets you enjoy the game on a modern HDTV. It's not available on the PS Store on those systems, so you'll have to have a PS3 to download the game and perform the transfer.
