The best part of ability is availability. If Harvin was available for the full season, the Vikes would have been better, possibly having a different playoff seeding and Harvin would have been in contention for offensive player of the year with his teammate. Additionally, Peterson wouldn't have had the lucrative stats that he put up in Harvin's absence.
Another factor is visibility. Jones was involved in a bizarre, clutch, game-winning play that had plenty of air-time. And players vote on these lists. They don't have the time to know players on teams that they wont play during the season. Fans have more time and less focus on their upcoming opponent. So generally fans have a better grasp (other than Tim Tebow fans of course).
So by that logic, Golden Tate is in the Top 10. Nice...
Taking it a little further than I contended, but I get your point. If the Seahawks had won the SuperBowl, that play would have had ridiculous airtime, and I wouldn't be surprised if he did crack the Top 100 list. Marginal players make this list every year; John Kuhn was on the list last year and Donovan McNabb was the year before.
For the record, Harvin is way better than Jones, the contract speaks for itself. What I was saying is that if Harvin had been healthy for a majority of the season, he would have been higher on the list.