I see your point, but I'm not so sure that he could've been that TRANSCENDENT level star. He clearly would've been much bigger than he is now, though (mostly because they wouldn't have fukked his character up, and they might have given him a heel run at some point if and when he got stale to the audience).
And the answer to your question is of course not. They could've stretched THEIR runs out and been more popular than Cena, and they MIGHT have gotten as or more popular than Cena in Cena's own era (Cena was pretty much the last guy to get really good booking on the way to being a main event level guy. Sucked afterward to diminishing returns, but '03-'04, maybe even early 05 Cena was fine), but after 2005 or 2006? Never. Tell me, who's been built in WWE solely after 2005 and not gotten sabotage booking for no reason? For that reason alone, they wouldn't have been popular. They might have been stars, but not even close to what they were in that 1996-2001 era of wrestling.
Really, the only guy purely built after 2005 to even get to Cena's level was CM Punk, and that was a total fluke, by all accounts.
Ugh.

So annoying to even think about.