Foobar's the only realistic alternative because it's the only one, that I know of, that supports the full gamut of plugins written to play video game/ancient computer audio files. Mostly because guys like Neill Corlett wrote all those plugins ~15-10 years ago when your only choices were Winamp or Foobar.
And of course, if you're on Unixen, XMMS is pretty much a direct clone of the old Winamp (and used to even use the same skin by default).