If you had fond memories of playing Streets of Rage 2 on the Megadrive - or more recently on the PS3/360 compilations, then this remake is well worth a look. It uses the same graphics but runs on the PC and has been heavily tweaked - new music, branching levels etc. Take a look and you'll see how cool it is. It's a two hundred meg download but well worth it.
Here's a YouTube vid of the older version - http://www.youtube.com/watch?v=8RCbkeunK3Q