I'm not sure I understand the question. I rank lots of guys above those three in a dynasty league... AP, Martin, maybe Trich, Foster and Charles and possibly even Morris... maybe.
As for those three...
Rice is pretty damned reliable but I imagine they start to spell him off a little more and try to keep his carries around 200-250 going forward with similar sort of 60-70 receptions. For me he has another good year or two of solid RB1 before dropping to an RB2 like Forte is looking this season.
Spiller looks poised to hit his stride this season but the injuries are a concern. The guy has crazy upside though and, if he remains healthy and can keep up anything near the YPC he had last year, he should be a top 5 RB for a while.
McCoy is the biggest risk of the three here and to me his ceiling is below that of Spiller but maybe higher than Rice's. This past season's production was okay from a yardage standpoint but just appalling in terms of TD's. Obviously the whole situation in Philly has changed but rarely does tat bode well for instant and dramatic improvement. I expect similar struggles to start the season before a solid finish under a new HC who might realize who the best talent on the field is (McCoy I mean).
With all that, I would rank the three guys: Spiller, Rice, McCoy but the top two are interchangeable depending on how much risk you want to take. Rice is a much safer pick but I think Spiller has the better chance to but in that top tier for the next couple years.