Rory will win many majors during his career. He was just too inexperienced to deal with the back nine on Sunday, teetering on the lead, at arguably the most pressure-filled tourney. When Tiger did it at 21, he may have had more fortitude, but he also had many more strokes to blow.
As for Tiger's persona on the course: I tend to agree that I dislike rooting for folks who act like douchebags but I really believe that Tiger doesn't feel personally entitled to a smile until he cracks a new tourney. I went on a match losing streak in college and on the day I turned it around and finally took a win, I didn't smile until the win despite numerous great shots. I didn't feel entitled to any pleasure until I delivered the product I thought I was able to deliver. And this coming from a guy (me) who doesn't take himself too seriously and is generally a happy-go-lucky fellow.
If he wins one, I bet we see him reveling in more shots during play.