Why do you wish he wasn't in the band?
Lake and Palmer are great, but Emerson is the main attraction. Watching him perform live is a spectacle in itself, his stage persona, his gaudy outfits, the guy's hysterical.
As goofy as he is though, the guy is an incredible keyboardist.
The guy was like Hendrix on the organ, he tried to get as much noise out of that thing as possible. I guess that kinda thing is only cool when guitarists do it though.
I also love his piano work, the piano solos from Take a Pebble and Karn Evil 9 2nd Impression are fantastic. And of course the moog solo form Lucky Man is kickass and played a major role in popularizing the use of that instrument in the prog genre.