I think Reigns has the look and can wrestle pretty well, but I don't see the personality at all. I know he's had some garbage written for him, but we're almost 5 years into his career and we still don't know exactly what Reigns personality is. He just seems like "some dude" and that's it. The best gimmicks are usually just the exaggerated version of yourself, so...who is Reigns?
I think he's got the personality to be the company guy, like he normally comes across well and treats the kids well etc, and seems genuine and hard working. He's probably a pretty intense guy as was an athlete prior to WWE and as a wrestler probably has that intense warrior type side based off his lineage and charecter. I don't think he's The Rock type guy though, Rock was amazing on the mic and was a born entertainer, I don't think Reigns is that, however do you have to be? I don't see what makes Cena a superior charecter than Reigns, he'd probably be more in that mould than a Rock, the next guy it's not always what the fans want it's who can do the job. The problem with Roman is the booking and now they've put him in a tough position where he has to win back a certain type of crowd, the female fans and kids love him though just like Cena, it's the hardcore demographic he struggles with more so it's if they find a solution to overcome that. As I said if he's booked right, possibly as a heel first (then he's meant to boo'd) and shows intensity and more charecter and then when the fans really start liking him again could turn it around, alternatively in this day and age can there be a guy who's gonna be pushed like that that's universally loved, the fans are more rebellious now. Roman could also potentially do other things that could elevate him too, if he can act he may get those type of offers too, he has the look, will have a female fan base, he seems like he's good with his kids too, there's a few things he could do, he also from what I've heard does have some attitude and personality but struggles when somebody writes his shyt, apparently organically he's quite good. It's all in the push too, if WWE drop the ball it won't happen but if they decisively say ok this is our guy no matter what anybody thinks and let him earn his due through stellar performances I still think he can be a big star.
Never know though, even someone like Big E, could he break out? He's young, strong, real athlete, has really developed his on air charisma and personality, can wrestle, with a solo run or a title run 1 day I wonder what he could do, he's got something interesting I think, liked him ever since he debuted, even though at first it was more in ring, now he's doing well promo wise too...