Even after all these years I still remember pokemon has one of the best dubs ever, team rocket comes up with the funniest (English) puns around which I think would not have been the same if it was in Japanese.
Anyway it's true though, most English anime dubs are horrible. The latest one I saw is gundam 00, I was watching that Hallelujah torture scene (dubbed) from season 1 and godDAMN it's making my ears bleed. Another horrible dub I can think of is Death Note when Raito said "I will take out a potato chip... AND EAT IT!" or something like that... BLEEEH it sounds really irritating. Good dubs exist but are quiet rare.
However strangely enough I do find english dubs in Japanese RPG games to be generally well done, such as; suikoden 5, valkyrie profile 2, tales of the abyss, persona 3 (Aegis's robot accent was done quiet well) ect
I reckon it's usually better than anime voice actors.