Anime and American Anime are two different things. American Animes are nearly always created to leech off of other franchises, with little to no original ideas in them. In almost all cases, they are made for the sole purpose of making money off of small children - and this is the reason why they are generally so horrible. Japanese anime, on the other hand, appeals to children as well as adults, and the more mature ones are treated even more seriously than the serious dramas we we see here. I'm not saying that American Anime is always horrible, but it is almost always horrible.
I know that Cowboy Bebop has very good voice acting (especially for an anime), but even though it is good, much of the original meaning of the words is lost. Not only do the characters sound different, resulting in different personailities (such as in Faye's case), but many small things are ignored. With the Japanese (and generally with subtitles), you end up getting the full meaning, with nothing cut out due to making the voices match the characters, etc.. This kind of thing happens in every single anime there is, unless it's written in English in the first place.
Oh, and Trigun has horrible English voice acting...