Well, it's less a "remake" and more of a hugely expanded, mostly new game. Remake, built entirely using new code, contains 103 stages, and all the playable characters from Streets of Rage 1, 2, and 3 (with new abilities), along with new characters. New enemies based on the Game Gear games and cover illustrations have been added to the lineup of punching bags. Boss Rush, Volleyball, AI partner mode, and other extras are also thrown in. Oh, and there's a level editor.
Check out a video of an earlier version after the break, and download the Windows game here before Sega's lawyers hit the Streets.