What does it accomplish by booking Sting to lose a match? It would make him look bad. That gives the impression that big era stars of yesteryear can't hang with the current era. And vice versa. And what does Cena accomplish by beating Sting? He's already beaten all the big stars of his era plus the Rock. That was his cherry. Does he really need another?
For further reference I present the Jack Brisco versus Danny Hodge conundrum of the 70's. A dream match of epic proportions back then. But it wasn't plausible for any booker so it wasn't done. This is similar. Cena looks weak in loss and no more stronger if he wins, and Sting looks weak in loss and no more stronger if he wins.
A Cena heel turn? I would exhale.
I disagree about booking Sting to lose a match would make him look bad. Sure, booking him to lose
all of his matches in a WWE ring would certainly make him look less than stellar, but booking a match with the proper opponent, and having them tell a compelling story in a plausible manner like only seasoned veterans like this can, this doesn't have to make anyone look bad. In fact, if done properly, it makes both guys look like a million bucks.
Sting versus Triple H, if indeed that is his first match, should end in a victory for Sting. Will Triple H look bad in the process, or will his legacy be tarnished in any manner whatsoever by the defeat, absolutely not. Both of these guys know how to tell a story. They understand ring psychology. The comprehend their own relative strengths and weaknesses, and can exploit their pluses and minimize their minuses. Both of these guys would come out looking great in my opinion.
Sting versus the Undertaker could be the exact same thing. Different outcome, mind you, but just like Triple H would not look weak in defeat against Sting, the Icon would not look weak against the Deadman if he were to lose. This would be all about the spectacle, all about the hype, all about the anticipation, and both of these seasoned veterans would tell a story like few before them. Sting would not have his legacy compromised in any manner by going down to defeat at the hands of the Phenom, no more than HBK didn't (either time), Triple H didn't (either time), CM Punk didn't, or pretty much anyone else for that matter.
Losing to John Cena would not tarnish the aura around Sting either. Cena, much to many people's chagrin, has defeated pretty much everyone who has stood before him. He's the face of the company for this generation, has been for some time now and will continue to be so for the forseeable future. There's no shame in anyone losing to this man. I would, in fact, argue that it's unrealistic to see someone even of Sting's pedigree, come in and beat John Cena in his prime. Cena is adept enough, despite his naysayers, to emerge victorious in this match, while being very respectful in the process, and could make Sting look fantastic in the process. Sting, even in the latter stages of his career, coming to the WWE when no one ever thought it would happen, and taking the face of their company right to his limits, coming up just a smidge short in the process, I think this would be both epic and realistic at the same time.
And could you please explain your final statement a little more, I'm not sure what you mean. Because as I've said on here a million times, I continue to crave the ever elusive John Cena heel turn. A month or so build up of mutual respect between the two guys, generation versus generation, WWE versus WCW, blah blah blah. At the end of the match, which Cena wins, the guys stand holding each other's hands in the air, and then Cena smashes him in the face and lays him out in the middle of the ring. Cuts a scathing promo on RAW the next night about how dare hecome into his company after all these years and try to steal his spotlight. That would definitely make me sit up and pay attention. And I don't think I'd be alone.