Why are you obsessed with Nadal and his results off clay? Yes, Federer and Sampras have more titles on HC, and what Nadal needs to do, hang himself for that?
For those who are interested, here are some stats for the top 4 by # of different events won and by surface:
Federer has won 27 different events:
12 Tier 1 = 4 slams, 7 masters, WTF
15 minor = 5 500, 10 250
20 on hard/carpet, 5 on clay and 2 on grass.
Nadal: 21 events:
11 tier 1 = 4 slams, 6 masters, Olympics
10 minor = 5 500, 5 250
9 on hard, 10 on clay, 2 on grass
Djoko: 20 events:
11 tier 1 = 3 slams, 7 masters, WTF
9 minor = 4 500, 5 250
14 on hard, 5 on clay, 1 on grass
Murray: 16 events:
6 tier 1 = 1 slam, 4 masters, Olympics
10 minor = 3 500, 7 250
14 on hard/carpet, 0 on clay, 2 on grass
Rafa doesn't come across as such a die-hard specialist in the sense that he has won almost as many events on hard as he has on clay, not the same # of times of course but still, his perf is much more balanced between surfaces than the other 3. Fed and Djoko are much more heavily slanted toward hard court than Nadal is toward clay. Anyway, the only one of the 4 I would call a clear surface specialist is Murray because of his 0 on clay. The other 3 guys have won something on every surface.
It's interesting none of them have won both WTF and Olympics. Agassi is still the only one to have done that (on top of his 4 slams and 7 masters) keeping his status as most versatile player in open era alive for now.