Foobar.
I've used Winamp 5 in the classic setting for a long time, and Winamp 2.xx for a long time before that and never wanted to switch to foobar because I too thought the interface was ugly etc. Then I dl'd the latest version to fool around with it, made it look pretty, and now am never going back. Foobar is THE player if you sincerely care about your music collection. I have a boat load of full classical albums ripped to Vorbis as well as rock, etc, and Foobar is just amazing when you customize the playlist display to your liking (which is super easy). And of course, it has a lot of "audiophile candy".
If you have a load of random mp3s off the internet and not full albums, use Winamp. If you rip your own music and have a nice collection, use Foobar.