Cena is easily the better overall wrestler, wrestling now is SO much more in depth and technical than it was in Hogan's prime. That isn't to say that there weren't amazing in-ring performers back then, but I think it is safe to say that wrestlers are far more polished now than they were relying more on gimmicky ideas like just being big (Andre the Giant) or being able to fulfill a stereotype (Iron Sheik). I think that has to do with the evolution of the business based on the groundwork laid by the legends of the past. Its like how LBs now are able to run faster than some great WRs from the past. It is just the natural steps taken in a given business.
That being said, I'll always love Hogan for his willingness to do two of the biggest things for the business, something that countless other legends would never do. First, the heel turn to form the nWo. This was so... jaw-droppingly amazing, it is tough to describe. It had a huge impact all around, it changed the business as a whole, and honestly... it took some guts. It is tough to imagine the "Say your prayers and eat your vitamins" idol from our childhood become a heel. Not only was he hated... but you loved to hate him. He was the same character, but when he was on the other side of the line, all of a sudden his "Brother"s and overall attitude worked just as well to make you hate him.
Second, he let the Rock beat him at WrestleMania. Even more importantly, he let him win cleanly. He even got his leg drop (Famously referenced by Lou Thesz that his grandmother could do a better leg drop) and let Rock kick out and then get pinned cleanly. Hogan wasn't great in the match, he didn't do some amazing technical matchup. But he was charismatic, he got the crowd behind him even though he was a heel and Rock was overwhelmingly popular at the time, but even with the crowd cheering for him, he sold the younger guy and passed the torch. I think that says a lot about Hogan as a worker and a person. Bret Hart didn't want to sell Shawn Michaels because he didn't want to lose infront of his fans. We hear about people all the time who won't sell out for the younger guy. Hulk did what was asked. Ya, he stuck around for too long afterwards, but I think the symbolism was clearly there.