Where's DGB on this list OP? I think you can safely slot him ahead of any of your 15 guys, and MAYBE above Watkins...If we're looking purely at on-field.
I don't think you can safely do that at all.
Best college season:
Brandin Cooks - 128 catches, 1730 yards
Davante Adams - 131 catches, 1719 yards
Sammy Watkins - 101 catches, 1464 yards
Allen Robinson - 97 catches, 1432 yards
Mike Evans - 69 catches, 1394 yards
Odell Beckham - 57 catches, 1117 yards
Kelvin Benjamin - 54 catches, 1011 yards
Dorial Green-Beckham - 59 catches, 883 yards
If we're looking purely at "on-field" achievements then he has no case for being ahead of these guys. You can argue that he has more potential and/or talent than these receivers and that he would have had a huge junior season if eligible, but that's all questionable. Nevermind the fact that character issues are a real tangible thing. The guy got booted off the team at Missouri and bolted Oklahoma without playing a down to chase the money. Neither one of those things really reflects well on him.
DGB seems to have the potential to become better than many of the players on the above list, but when you weigh all the variables, I don't know if you can comfortably take him ahead of any of them. Maybe the second tier guys like Adams and Robinson if you're not sold on them. He's a big time boom-or-bust proposition IMO.