1. Being fast do not make you a prodigy.
2. Intelligence? There are several ninjas who displayed better intelligence than him and wasn't hailed as a prodigy.
3. Skill? Flying thunder god style....I'll give you that. But I would've liked kishi show us a reason why it wasn't easy to learn that style.
4. power? what power?
I'm not saying he sucks or anything, I'm just saying he doesn't live up to the legend that the manga had created for him.
prodigy:
noun
a person, especially a young one, endowed with exceptional qualities or abilities.
"a Russian pianist who was a child prodigy in his day"
synonyms: genius, mastermind, virtuoso, wunderkind, wonder child, boy wonder, girl wonder; More
an impressive or outstanding example of a particular quality.
Speed can mean your a prodigy if you excel at it. As for power, I mean his overall deathly reputation. But the fact that he was hailed as the fastest shinobi in history, is more than enough to be called a prodigy as explained above.
btw Usain Bolt is called a prodigy by many of his peers