Steven Blum is my choice if only becasue he is my favorite career voice actor of all time. He did awesome with Vincent, but he does great with everyone he plays...
Spike (Cowboy Bebop), Char Aznable (Gundam movie trilogy), Mugen (Samurai Champloo), Makoto Shishio (Rurouni Kenshin), Ken (Street Fighter Alpha), and countless other characters in countless other anime titles and video games... he's even leading the voice cast in the new X-Men TV series as Wolverine (a character he's played in the video game adaptations for a long while)... he's just absolutely perfect in most everything he does.
So yeah... Steve Blum was definately the best AC voice actor... but there were others that were okay... however some of them had offset emotional strains on their voices that didn't exactly fit the situations, and what not, and that detracted from the quality of the overall English dub performace... but... egh... what can you do? It happens often nowadays... but at least its not as bad as some of the horrid 80's voice work... ACK!