Can't beat Karthik. Passion, history, and an excellent sense of drama and humor. I watch some old regional videos just to hear his intros occasionally (yes, a bit weird, I know, but they're also some awesome matches).
Of course, I also have to put an honorable mention to Yoji Shimizu, our emcee at Lake Superior/ North Star, if only because his shirts are cool and he has those cool pants, as well as Tyler Olds, who brings Northern Lights and 10,000 Lakes to life. Might be a little bit of hometown bias there, though
.
As shameful as it is, I don't typically listen to game announcers so I don't have much of a judgement to make there.