I'm running another poll (general boxing forum) for best commentator, and Merchant is currently leading in the votes....
It's strange but the two fights that stand out for me with great commentary are both the Leonard vs Hearns fights, maybe because I had "The War" on VHS.
Gil Clancy was the best "expert" commentator, and when he teamed with a play-by-play broadcaster like Tim Ryan AND Angelo Dundee, it didn't get any better. I'm also a big fan of the Bubblegum Kid on commentary.
I would pick Manny Steward(rip). I really enjoyed listening to his analysis of fighters and fights. He was very articulate and his knowledge of boxing was unparalleled.