Neither Ray Lewis nor Mike Vick should play in the NFL. And just because Lewis was welcomed back (IMHO, a wrong decision), does not mean that Vick and everyone else who commits terrible crimes should be. I do not know much about Lewis, but Vick’s behavior was sadistic, that of a sociopath.
I think there's a difference between having a hand in stabbing a person to death and animal cruelty.
Vick did do time for it (Lewis got off scott free), and has lost his fortune and his already shaky reputation. I'm not sure that he should completely lose his ability to make a living.