>> What else would you call one of the top math students at cambridge?

I would call him a good, hardworking student. (At least that's what we'd call it in Singapore ;) Coincidentally me and Xu went to high school at the same time in Singapore)

If we labelled everyone who did well in the undergraduate curriculum as prodigal - the word itself starts loses its meaning.

Let's take the top 20 universities across the world (harvards,mits, tsinghuas, iits etc.) and take the top 10 graduating students from each class (math, physics, etc.) => are we saying that the world is producing 500-1000 prodigies every year?