Parera is not as good on hard as on clay, Federer is not as good on clay as on hard. Agree with the rest though
Roger is a very good candidate for this category.. I mean he has only really lost to ONE player. If Nadal wasn't in on the scene and Roger won all those titles on clay, I don't think there would be many doubting his ability on clay.
But if you insist he isn't a good choice, like previous posters have posted, Djokovic/Davydenko are good picks. While Soderling hasn't really had big success on clay in MS events, we all know his success at Roland Garros, so he could be a recent candidate for this question.