Xander Mobus has embraced it the most and has the most fun with it. I'm not the biggest fan of the way he says some characters, namely Puff, Dorf, Cloud, and Corrin, but he's still good. Harrington and Manning both have great energy, though the Melee announcer is a little subdued.
It's hard to pick one. I like particular lines from each one. Harrington's "failure" is good because he sounds so disappointed in you and who can forget Manning screaming the name during the title screen.