At the end of the day, its gonna be an interesting argument.
1.- What's more impressive:
-Turn business around after 30 months of declining business for a company that couldn't find their next big star? In a context of a wrestling business that wasn't nearly as global as it is today, and that was still getting used to WWE being a monopoly. That's what Cena did from 05' to 07'.
-Become an instant draw and an undeniable white hot babyface after leaving the company as a midcarder that never meant a thing for business? And take the spot of the n°1 babyface like no one else could in the company for two decades. And not only that, be able to sustain that level of impact (in both business and crowd reaction) for more than 2 years in a wrestling promotion that had become an expert in destroying its own babyfaces momentum at any chance that got. That's what Cody's done since he went back in 2022.
2.- Who had more support?
-Cena had WWE's monopoly and its marketing machine going into overdrive to make him their next crossover superstar. Roster wise he had Batista's rise, that also helped business a lot when he got first title run, but that didn't last long. He had a ton of veterans that were big stars in wrestling's biggest boom (Attitude Era) but he didn't really work with them for like 2 years into his main event run. "WWE sells as a brand" started during Cena's run.
-Cody had The Bloodline storyline becoming the best and most succesful angle WWE had in 2 decades, which started to turn business around and starting up a mini boom. It was Cody who was instrumental to help that momentum turn in the legit boom we see today too. Roster wise he has an incredible pool of talented wrestlers, though none are "icons/legends" like Cena's roster. "WWE sells as a brand" had been establised for more than 15 years once Cody became a main event act.