I know I am in a distinct minority about this, but Johnny Carson just never did much for me. I never thought he was funny, and I didn't like "The Tonight Show" when he hosted. I don't like Jay Leno, either.
Give me David Letterman any day. And from what I've seen of old clips, I prefer Steve Allen to Carson as well.
There's no denying the impact he had on TV and culture in general, but I, for one, just don't get it.