In general I don't like dubs but some that I've seen are actually quite good:
Neon genesis Evangelion : Asuka is awesome in these
Cowboy Bebop : pretty good as well
Gundam Wing : I saw the dubbed version first so I was used to those voices, this might explain why I like it (a bit) better then the jap version
Worst possible dub ever : Ah! My Goddess : Belldandy sounded completely wrong, I just couldn't stand it, she just lost her completely innocent atmospgere with it ...