Cena has, IMO, been the victim of a huge mistake (yes, another one) by the WWE Creative Writers and Board. As soon as guys like Stone Cold, The Rock and so on left the WWE, they needed someone to fill that gap left by them. Basically, they saw Cena, someone with Charisma, SOME wrestling ability and obvious potential, and immediately shoved him out on the big stage. Maybe just a year, or even 6 months, in OVW or DSW and we all might be posting here about how great the guys in ring skills are. But NO. Of course. The WWE have to make lots of money fast. And it worked. He drew crowds. Merchandise was bought. People were Chaingangers. Some still are. But a heck of a lot aren't. Eventually people became just plain BORED. And when you're bored with someone, it sometimes happens that you search for faults. Now, justifiably, people are critical of his 2 year stay around the WWE title, his in ring ability, and his gimmick. Maybe, just maybe, if the WWE Board had stopped themselves, calmed themselves down and let time do it's thing, Cena would have been a long term project. Now, it's basically over. People still like Cena, and no disrespect to anyone out there who does. But to me, all the evidence points to him being two things: overpushed, and overrated.
I don't think it's fair to compare him to guys like HBK HHH Edge or the late great Eddie Guerrero. Let's look at each one. HBK. The total package. He can make you hate him in 1997, then love him not long after. He can fly to the ring on a zip line, put on fantastic matches, and bring life into a dead crowd. HHH. The Game. Multiple Time World Champ. Has carried this company (With some help) for many years. What more can I say. Edge. Possibly one of the best heels ever to grace a WWE ring. Has the ability to win Best of Night award with a Mid Card match. The guy is really very good. Eddie. The sheer reaction after his death says it all. It is not often you find anyone who can go with these guys. Cena tried, and IMO, almost succeeded. Unless he goes back to train at OVW/DSW, which seems unlikely, he never will.
Once, the Cena train was motoring along, but soon people started getting off, and now it's breaking down.