Finding sites which review dubs in a very fair light is a rarity, especially on the internet. There, people can post all kinds of opinions, no matter how ridiculous they may be. Here are some sites which I find totally offensive and a slapping insult to dub fans. Be forewarned!
http://www.fuzakenna.com/ -- "There are no good Anime English dubs"? Seriously? How can you expect me to believe that? Seeing this entire post made me angry; OK, so he DOES acknowledge Vic Mignogna's performance as Edward Elric in Fullmetal Alchemist, but everything else about this site? Don't even bother wasting your time.
http://ghiblicon.blogspot.com/ -- I really, really dislike this website. The owner of this place practically hates every dub Disney has done except for Spirited Away, Howl's Moving Castle, and Ponyo. To say that they're consistently horrible and that Ghibli should only be in Japanese is both a very unfortunate, one-sided argument and a slapping insult both to fans of these movies in English as well as Miyazaki--he personally had NO PROBLEMS WITH ANY OF THEM. Yes, this guy does make recommendations to obscure movies, but dub fans, AVOID AT ALL COSTS. And as a sidenote to a certain comment I received recently about how this site makes "excellent" reasons why the dubs are "bad"—to me, a person who makes comments such as "I am firmly against ever dubbing a foreign movie" is NOT someone whose reasons I would consider valid for any reason. Especially since so much of his "arguments" are over such trivial issues.
Dub Haters at MyAnimeList -- They even dare to put a cross on Crispin Freeman, one of the best voice actors of all time. He was terrific as Spark in Lodoss TV, Tylor, Zelgadis in Slayers, Regal in Tales of Symphonia, and just about anything else I've heard his voice in. That should tell you something about this place. Luckily, this place DOES have a Dub fan section.
And there are lot of others that I won't even dare to mention.
I'll be honest. I confess to hearing some truly hideous English tracks such as Demon City Shinjuku, M.D. Geist, Love Hina, Roujin Z, and the Streamline distributed dubs of Akira and Laputa -- both of which are thankfully available in newer and more improved versions courtesy of Geneon and Disney, respectively. But a good majority of the dubs I've heard (which may not be as many as other "anime experts" declare) are at least passable to great. This is why sites such as these only compel me to stand behind my position as a dub fan.
At the same time, though, it is unfortunate to see how narrow-minded a lot of internet Anime fans have shown themselves to be when regarding dubs; a good many of these so-called "unlistenable" dubs have performances that naysayers are truly missing out on. (Seriously, half the time I listen to said "horrible" dubs makes me wonder if the "reviewers" in question saw the same English version.)
Ultimately, I shall say this: whether a dub is good or bad is dependent on the viewer. It's totally subjective. There is no "only way" to watch Anime; nor are there any rules for dissing English dub actors and fawning over the Japanese actors, talented though they may be. Dubs, and translations, for that matter, are a form of art. They are here to stay, no matter what purists may feel about them. Fans who watch dubs are just as much Anime fans as sub-fans are; there's no superiority contest. It's just a preference.