I mean, I would probably have highlighted his starring in Top Secret! first, considering it was his break-out role, and he is excellent in that film. And also that Top Secret! is an excellent film, that too few people have seen.
I think that his best role was Doc Holiday in Tombstone. He was the embodiment of the flawed wild west gunslinger.
Watched it as it was just released back then and loved it, a lot more than Airplane and other similar comedies.