Is Anderson Silva the best MMA boxer ever?

One of the best, sure. There's a lot of guys around that were orignially boxers before MMA that compete, and other guys with excellent hands but some flaw in their game that prevents them from becoming as good as the best.

 

Pulver was decent. Textbook in outboxing Gomi for a while despite being in an MMA match, and did have a pro boxing career.

EDIT: Although as I rewatch it for the first time in over a decade, Pulver vs Gomi is slower and less impressive than I remember it. Huh. How times change.

 

Rampage Jackson? Igor Vovchanchyn