English VA’s aren’t necessarily good - they can be awful. The more important point is that Japanese VA’s aren’t as good as they seem. That’s becuase there’s a disconnect. We don’t actually understand, viscerally, what they’re saying. Essentially we hear some neat sounds, and we read some words, but our brain doesn’t directly associate one with the other. Emotional range or veracity is generally lost in the translation - meaning it’s almost impossible for us to judge whether a Japanese VA is good or bad. But since there are plenty of English actors which are indeed bad, the Japanese experience is often considered better.
To be honest, anime scripts are often so corny that being shielded from their full impact is often the only way to enjoy them. ^^; But a really good anime can be enjoyed in English. Slayers was excellent with this, because it joined a great cast with a script which went through very professional localization: the script is not word-for-word from the Japanese, but calculated for an American audience. The end result is something us Westerners can actually enjoy for what it is.
In my own opinion, I’d rather have a mediocre (i.e. not horrible) English dub than a Japanese dub. I feel it’s much more “accurate” to my own experience… and of course there’s the fact that I don’t have to keep jumping back and forth between subtitles and the action.
There are exceptions to this, of course… animes that are full of Japanese references (such as Samurai Champloo) I’d rather see in Japanese.
While I don’t automatically shun English dubs, I usually prefer Japanese. Because I don’t register the sounds as words, I can’t necessarily identify the inflections and variations in tone that I naturally pick up in English.
“I can’t wait to get started on this adventure!”
sounds so much better than
“A rushu mishi arabara areery ron pon!”
At the same time…
“Hello, my name is {ambiguously stupid sounding japanese name said in english}”
sounds much worse than
“{bunch a shit I don’t understand that is too high-pitched if female, and all the same if male… deep and indignant.}”