Street Fighter Zero 2
This second installment of the Zero/Alpha series is what the first one should have been. Not too much has changed as far as gameplay goes (the chain combos were taken out), but the graphics and backgrounds have been improved greatly. 5 new characters were added, plus the 3 hidden ones from Zero/Alpha 1 are now directly playable. There are a few hidden characters in this version, but nothing great, just a few new outfits and extra moves added to the already playable characters.
The sound is a bit better too, and the addition of Custom/Original Combos add a bit to the gameplay. But overall it's just a better version of the 1st game, and not really a sequel. This game should have been the only one released, because it adds so much up on the first one, yet takes almost nothing away from it.
If you don't have Zero/Alpha part 1, and you like Street Fighter games, this one is great. However, although it's a big step up from the original, it's not really a different game, so if you didn't really like the first one, stay away from this one.