Harrys flying skill was complemented by Victor Krum himself(book 4), at the time the best seeker in the world, as well as ludo bagman, the head of the magical games department, and sports caster. (no book with me at work if anyone can help me out with edit quotes.)
Another interesting point, is that most likely star players on house quiditch teams, would be drafted by the professional leagues as their was no "college" were typically we see pro's drafted from. With other good players probably getting drafted by minor league teams. We can speculate this because Krum himself was drafted while still at school.