Cena isn't a bad wrestler at all. Now he's not the best ever, because his full move set isn't really impressive, but it is good. People tend to forget that Cena isn't the worst wrestler ever. For some reason wrestlers like Ultimate Warrior, Great Khali, and Giant Gonnzales escape their minds when the topic of Cena is brought up. Even with his limited move set he's still better then them, so even limited Cena isn't the worst wrestler ever. I think the people who really dislike him are the ones who just want to see their favorite wrestlers on top. It sucks seeing someone you don't like get all this stuff, meanwhile your favorite is stuck doing midcard stuff. IT probally annoys them, and they point the finger at Cena because he's the superman guy who goes over everyone and whatnot. I think most of the hate though is just a bandwagon hate.
Most who hate him haven't really seen his matches, or they will see his matches and not care. Like his matches with Punk, people seem to ignore Cena and praise Punk, even though it was both their hardwork to make the match look good. I've seen Cena do impressive things, and still most of the IWC just blindly hate him and gives him no credit where credit is due. I know that Cena is lazy, and the superman booking is really tiresome, but it's whatever. I think Cena should just put young guys over already, it would be a much better use in my opinion, and it would be a better choice then a heel turn since he would be making young talent look actually good instead of a simple character change that 30 year old men would like.
It's whatever though. As I said he's a good wrestler, not the best by any means, but he is far from the worst.