He has good mic skills, I will not deny that, but the gimmick he's in is terribly unfunny. All it is is an accent and a quip or two... Ooo, yeah, real great.
You get him in a better role, drop the accent and make him a decent heel, then I'll say he's good. And he's in trouble if they leave him in the Santino gimmick for long, otherwise he's going to end up like Eugene, a comedy act that's rarely used or terribly mis-used.
As for Cena, I'm not saying Cena is shit, in fact I'm a huge supporter of Cena and think he's the best thing public relations-wise to come along in a long time. But he's in a terrible gimmick and he's terribly canned. He needs to let loose, otherwise he's just another wasted talent.