Hmm… for 4Kids voices I liked:
Robin: Veronica Taylor is one of the few actors in 4Kids who has talent. The accent was a bit much, but I was only able to really notice it when she used stereotypically southern words like "dally". Like Kazu-kun said earlier, Taylor was able to portray Robin with elegant yet cynical inflection. I have to give credit to Stephanie Young, though, since she's good at that as well.
Zoro: His VA was another one that sounded good. His new voice is great, too, but his 4Kids one sounded much closer to Zoro's age (it's 19, isn't it?). He was able to emote much better than most of the other voice actors, but Sabat's voice works great. He was my first choice for Funi Zoro.
Chopper: Lisa Ortiz is in the same boat as Veronica Taylor; one of the few 4Kids actors with actual talent. Chopper sounded great in the games and at Drum Island, but it went downhill at Alabasta. However, I still found it preferable to Chopper's Funi voice, which sounds more like a screaming idiot than anything, since he's CONSTANTLY screaming in Funimation. I think Chopper's new voice is the only one I actually dislike among the Strawhats.
Vivi: Personally, I prefer Caitlin Glass (sp?) as Vivi, but her 4Kids voice wasn't too bad. Her voice was incredibly stiff most the time, but there were a few times when sounded pretty decent (Grand Adventure being a notable example).
Buggy: I don't feel this needs an explanation.
Bon Clay: The ebonics accent actually worked here, and it sounded just as goofy and queer as Bon Clay's appearence would suggest. He even made the idiotic puns sound less, well… idiotic.
Mrs. Double Finger: I actually liked this voice. It fit her very well in my opinion, and sounded pretty good aside from the occasional needle pun. In fact, to the best of my recollection, her Funi and 4Kids voice sound very similar.
That said, the Funimation dub cast is far superior. I would take them over 4Kids voices any day (except Chopper). The voices I posted were just a few good actors in a vast sea of mediocre garbage.