Best i don't know if there will ever be a person that we will always agree with and whihc will just work well with the match itself, the best comments that i heard where from mats wilander (at RG).
The worst? WELL THE LIST CAN GO ON FOR EVER!
But my award
goes to a polish eurosport commentator, called Adam Chojnowski, the man is i think 70 or something like that, his voice is extremely hoarse and he doesn't seem to know much, all he can do is just read the stats from wtatour.com and comparing with tennis fans he doesn't seem to follow the news too well (or his memory is going). He really sounds like he's going to die in a second and he seems to sleep sometimes, cause he doesn't say anything for 2-3 minutes.
One thing he said is : " "
Eurosport int. commentators aren't bad especially if you compare them with the polish commentators (who are so full of themselves now that we have Radwanska, who are overly opinionated and the prize money and all these extras are more important than tennis itself).
The worst thing for me is when the commentator keeps on talking while the match goes, esp. if it's two of them having a conversation.
I've heard french commentators, american and australian ones and they don't seem to be that bad.