In some cases, it's true, but not usually. Just off the top of my head GTO, One Piece, Evangelion, Yu-Yu, Berserk and a slew of others are dubbed horribly. Just massacred. Not to mention the Japanese voice actors tend to do a better job most of the time, with the english actors just "phoning it in", as they say.
There are exceptions of course. Many of the showa Adult Swim licensed first is very good in English. Like BeBop, GITS, Trigun, FMA. Recent years have gotten better. Also worth mentioning, some DVD subs are also inaccurate on older anime (basically just a direct transcript of the english dub track), thus the reason many of us prefer fan subs, so on those, watching English or Japanese makes no difference, except in acting ability.
And subs don't detract from the anime once you get used to using them.