#4 Finn Balor

Finn Balor and Brock Lesnar are the only two performers that have never lost a Universal Title match. Balor had to give up the title due to injury, and has yet to get a match for the belt. Winning back the strap at 'Mania would be a picture-perfect redemption story, and those two could tell an awesome story in the ring.
So why isn't Balor higher on the list? Because it looks like he's not higher on Vince McMahon's list. It was surprising enough that he won the belt at SummerSlam 2016, but upon his return, it seemed like a return to the status quo for WWE: a small wrestler that's super over with the fans is near the top of the card, but isn't champion.
Cody Rhodes' uncle is a WWE Hall of Famer. More details HERE.
Sadly, after this past RAW where he was a transition guy in the Gauntlet Match, it doesn't look like that will change anytime soon.