I see Cena on a lot of talk shows, podcasts, behind-the-scenes videos of talking about legends, and one of thing that sticks out to me is just how much Cena seems to now understand the psychology behind booking, but even recently with his feud with Austin Theory, he doesn't actually understand how to apply this knowledge to his work. Its been an issue throughout his career, he's never truly elevated a talent, and is usually just a stepping stone if anything to something much greater or bigger.
Did people benefit from beating him? Not always. On the top of my head, the ones I can think of are
>Lesnar upon his return and Summerslam
>Seth's title run
>Roman's longevity as a champion
>Punk in MitB 2011
The first 3 are less the result of Cena's work and more of something started by someone else. Seth's title run was solidified by the entirety of the Shield and involved numerous authority figures. Lesnar had already beat the Undertaker and it was the natural extension of his dominant return, Roman had already been through people like Bryan, Mysterio and Edge in terms of fan favorites, Cena would seal the deal in that respect of beating notably popular faces or just generally popular wrestling legends.
Punk is probably the one case in which you could argue he had a massive hand in creating a star. Cena had to be the opponent for Punk, not just because he was champion at the time, but because the entire angle of the frustration that they portrayed within the build up to MitB 2011 centred around lack of opportunity, being fed up with the state of the company and the pushing of stars that were overused. And I highly doubt it was Cena at the time who thought this all up and was the mastermind, let alone who understood what they were going for.
Cena doesn't get it.