I think Martin Landau's Bela Lugosi in 'Ed Wood' beat him for best supporting of all time. Kilmer did do the best Doc Holliday of all time though.
One hundred percent agreed. Landau killed in that role.
The first time I saw Tombstone (saw it three times at the theater when it came out and since have seen it so often I have the script memorized; I don't even know why I bother watching, but I do) my first impression was of Kilmer's overacting and dramatizing (and he was a sh*tty horseman compared to Kurt, Ike, Sam Elliott, Texas Jack, and Creek J.). Everybody oozed over Kilmer, but the bigger players who stood out most for me (out of a fantastic cast ... I mean, Billy Bob Thornton was perfect!) were Powers Booth as Curly Bill ... and Michael Biehn as Johnny Ringo (now there's a deserving Oscar), and a complete display of Kurt Russel's power acting -- the guy is the Miles Davis of acting. Understated and eloquent. He says more with one expression that most actors can say in 30 seconds of dialogue.
In retrospect, I think that it was the chemistry of Kilmer with Russell, and it worked perfect. But for a real Doc Holliday, the best portrayal, I still *ducking* think Dennis Quaid put it down in the otherwise pretty lousy Costner "Wyatt Earp."
And for what it's worth, I don't think Val Kilmer would be my huckleberry in a political contest.