The only player that comes to mind is Michael Irvin, only for the fact that they play as physical as it gets and both play with emotion.
Dez is really a different breed of cat at WR. He's an absolute livewire for defenders- his entire being is electric with the ball, and when he gets to speed and you can visually see defenders of almost any size not want any part of it one on one.
Dez CAN (now he drops some easy balls too, ala T.O.) make grabs that other players would deem impossible. His aerial coordination is superb, a la a young Brandon Lloyd, Chris Carter, or a mature Terry Glenn (who I think made some of the most amazing grabs ever by a Cowboys WR in his time in Dallas), but his explosiveness is far beyond those three players.
I've sat here for a half hour trying to come up with a player like Dez since 1980 and truthfully I can't think of one.
I'd say he's closest to Megatron (who I think is the overall better player), but Dez Bryant probably has greater big play ability than even he does.
To my mind he's an Irvin/Andre Rison hybrid. That's the best I can do.