I'm still rather disappointed I wasn't old enough to appreciate him when he was alive.
When he was alive, I knew who The Beatles where, but not Lennon. I was more of a Chuck Berry/Buddy Holly guy at the time. I vaguely knew who Paul was, but that was because my parents owned his Ram album since it had come out and played it constantly. But, I'd no idea who John was, and that still disappoints me a little.
He's one of those people I believe I would have been able to have a good, fulfilling conversation with. Not a "Garsh, you're great!" conversation, but a real one about life, death, politics, liberty, the pursuit of happiness and all that jazz.
Finally, had he been alive today, I would like to think he would have been one of the few to have the balls to object to the Iraqi War during the invasion, and that he really would not have been a Bush fan at all.