I don't watch a lot of anime, but I do watch a fair amount of foreign films. subs ftw.
the only time I've thought a dub was really good so far is Princess Mononoke I guess. and the dubbed dialogue for that film was written by Neil Gaiman <3.
usually, when a dubbed version even exists, though, it's dreadful.
I remember for instance, one time I tried to play Assassin's creed II in Italian because it seemed like it might be interesting. the Italian voice actors just weren't very good though, so I switched it back.