I'm going to go ahead and have to disagree with all the Golden Axe hate. The Turbo/PCE version has simply stellar music-- better than the original and/or Genesis version. The graphics are stylistically darker, which I actually kind of like as it sets a certain tone for the game. About the only bad thing I can say about Golden Axe is the game scrolls at like 10 FPS. Once you get in the groove though, you can easily look past this. I think it's a decent port that surpasses the original in some areas (music, cinemas).
Altered Beast doesn't qualify for me either as it's probably the closest to the arcade of any port up through the 16-bit era. Ditto for Street Fighter... I'm told the original arcade controlled just as badly (although I'll admit I've never played it).
Ninja Warriors is a piss-poor port, however. It seems like virtually zero effort was put into it. Same can be said for any of NAMCO's early Turbo ports (Ordyne, Genpei Toumaden, etc). NAMCO seemed to only put in effort about 1/4th of the time when it came to support of the console, actually.