It would be easier to name the dubs I don't like, since dubs are my default. I won't talk about that however, since that is counter to the purpose of this thread.
I like the Sailor Moon DiC dub and the Pokemon 4kids for all their cheesy glory.
I prefer the Nelvana* dub of Cardcaptors. Mostly because I like the tomboy characterization of Sakura better.
*which actually isn't the same as the terribly butchered version on kids WB
When it comes to Dragonball/Z I only like the Ocean Group/Blue Water and Harmony Gold dubs. I grew up with the Ocean Group/Blue Water dubs, so I the VA's over having Christopher Sabat voice half the cast. As for Harmony Gold I have only seen clips because it is rare, but it's not that bad, changed character names and was put out in 1989. So it's got retro-kitsch.
And Robotech, a lot of 90s shows cut out death and alchohol for T.V. This particular dub of Macross did not, and that's pretty impressive.
I don't know why but Pokemon 4Kids Dub really just seems to be a good dub. Of course, the edits were dumb/unnecessary, the replacing of music was not needed, and I know 4Kids botched up a few things here and there (TPCi is the exact same in this regard only to a slightly lesser extent but again only people who don't bash 4Kids without actually watching both dubs would know almost nothing has changed in any of these aspects)...but overall it's a nice solid dub in my eyes. And yeah, I love its cheesiness haha.
Kinda proved when 4Kids got their act together, they could do a good job. On the exact reverse end of that is One Piece.
As for DBZ, I'm a FUNimation fan but I do like Ocean Group's as well. Blue Water...not so much, for me, but some voices are solid like Zoe Slusar and Dave Pettitt and one thing that was better about Blue Water is that Mark Menza's music is not in it, rap and beats etc. The OST was better and was from Original JPN, but FUNimation rectified that on the DBGT box sets.
I've just had a startling revelation, a dub actually exists that I like better than the Japanese version. That's right my fellow Alt. Anime readers, by some miracle of god this dub actually come into existence. What is this miraculous dub, you ask? Supernatural, I like the fact that Jared Padalecki voices Sam, it's too bad Jensen Ackles didn't voice Dean though, but it's Supernatural, I just can't imagine it, live-action or anime, in any other language.
I heard Supernatural has a very good English dub. I think, and yeah so many people say this but, Cowboy Bebop had one hell of a good dub. Slayers as well, back when Lisa Ortiz voice wasn't flying everywhere in 4Kids and TPCi's dubs and her Lina Inverse voice actually sounded rigid, excellent, and distinct.