Well, disregarding the posts above me, I'll simply state my opinion and be on my way...
English dubbing doesn't suck. 4kids, for the most part, sucks. (when it comes to anime.) But even then you can't say they're all bad, because I think they did an okay job on Yu-Gi-Oh.
When I think of anime dubbing, what automatically comes to mind for me is "One Piece". Because it was just a terrible dub. It just takes me a little moment longer to consider things like Megaman NT Warrior and Yu Yu Hakusho, both anime's I absolutely cannot stand to watch in Japanese. It just makes me cringe to hear Kurama from Yu Yu Hakusho's voice in japanese. As much as 'Zolo's voice in english makes me cringe as well.
But then I also have to think about how amazing the new One Piece dub is, by Funi. They've saved One Piece, and I can't wait to see the new episodes. I might even start watching it in english, rather then Japanese, it's just that great.
So really, dubbing only makes anime less entertaining in the eye of the beholder. I personally think that dubbing jobs can make anime less-entertaining, especially jobs that are poorly done, but they can also be better then Japanese dubs. It really depends on what you're looking for.
So to answer the question the thread title presents:
Sometimes, yes, but not always.