Conan O'Brien > Everyone else on TV. Val Venis and Doug Basham included.

But yeah, I can actually kind of stand Jay Leno. David Letterman seems so arrogant. If I were killing off every other TV host for Conan O'Brien, I'd be able to do Letterman in easily, whilst Leno seems like a nice-ish guy. He was a douche to Zach Braff, though. Conan > Braff > Leno > Letterman.