I've got to ask: what happened to his face?

Recently I have been watching some later Travolta movies. I always found him a pleasing actor. Always thought he was a beautiful man in the 70s and early 80s.
But what the heck happened to his face now? I know that he's had hair transplants or something because his hairline is like painted on. But that aside, sometimes his face looks so different from what I'd have expected it to be when aged.
Seriously, what factors are to be counted when looking at him?