Well the difference between the Undertaker coming back once a year as oppose to the Rock is that the Undertaker has the streak, so nobody who he fights, it'll always be a good match, since they get a shot that only very few people got. And just because you don't want the Rock to come back doesn't mean you're a Cena fan, that's being ignorant to assume that.
As for what I think about him coming back, I think it should be to put over someone else. Put over someone, not to young though, I'd like to see someone like Wade Barrett, or Cody Rhodes, even The Miz. CM Punk vs The Rock would be great, but CM Punk is a multiple time world champion, I think it would be better to see those other guys pushed, just to add something good to their career in case of WWE being stupid enough not to put the world title around their waists(except The Miz). John Cena needs to start putting people over, not facing legends, Cena is already considered one of the best today, and is still young. Having the Rock vs Daniel Byran I would like to see too. It would be good to let Daniel beat the Rock, and since he has a motive because of the wedding thing, that would be able to take off. Plus he should get something for doing that 18 second Wrestlemania match, and fighting The Rock at Wrestlemania could redeem himself of that.
So in short, if the Rock comes back to put over young talent, yes. If he comes back to feud with Cena, hell no.