M.U.G.E.N is a freeware 2D fighting game engine.The engine allows for most of the same type of functionality found in most any commercial 2D fighting game, up to and including close recreation of those games' characters and gameplay.
this is the beta 2 release is great , hi-res sprites and great controls. must have for street fighter fans.
links:http://www.megaupload.com/?d=RN69PZ6K.