jrry32 refining his position:
I think your position matters because your position dictates what attributes are important. For example, taking your comparison for a DB vs. WR, Calvin Johnson is a freak athlete at WR because he's so big, so fast, so explosive and so good at going up and getting the football. However, he's stiff and does not possess outstanding short area quickness. At WR, those two attributes aren't that important for a guy with Johnson's skill-set. But at DB, you need to have loose hips and outstanding short area quickness imo to be a freak athlete. Whereas, going up and getting the ball...while a nice attribute to have...isn't something I'd care about as much for a CB when labeling him a freak athlete.
So yea, I think it does matter because certain attributes are more and less important to certain positions.
For example, I'd say Michael Vick in his prime is very arguably the freakiest athlete to ever play the game. Why? Not because he was the biggest. Not because he was the fastest. Not because he was the quickest. Not because he was the strongest.
What made Vick that for me is his combination of attributes. While he was only 6'0" 215, he possessed 4.3 speed, ridiculous short area quickness, amazing balance/body control and one of the strongest arms I've ever seen. Simply put, his physical skill-set was unheard of and completely unique. But if Vick had been a HB, he'd be an exceptional athlete but certainly not the freakiest ever. It was his incredibly rare arm strength that allowed him to be something we may never see again.
Too bad the guy just didn't have good work habits, character and football IQ.