I don't think that this is a question that can be properly answered by anyone who doesn't fluently speak both languages. For example, I have seen bits of American cartoons dubbed in Japanese on Youtube, but as for the quality of the dub itself, I cannot tell how good or bad it is since the voices just sound like....well, Japanese voices to me. I don't speak the language, so I wouldn't really know how someone who does fluently speak it would feel about that same dub.
Oh, and even though its off-topic, I once again just want to point out that I think that the English dub for Black Lagoon is one of those dubs that can be seen as superior to the original version. Its all opinion, of course, but I base my liking it more than the sub (which I watched long before the English dub even came out, BTW) based on the last arc, alone. I mean, aside from the fact that canonically most of the characters are actually supposed to be speaking English in the series (just like how certai anime cover stories in areas where people would normally be speaking a different language than Japanese), I just like the fact that I don't have to deal with any "Engrish" in the dub. When I was watching the last arc subbed, what started as some laughable bad English voice-work from the seiyuu of the series, quickly turned into a really big annoyance thanks to it being so over-used in that arc (IMO, anyways).