#3 Bobby Roode

The 'Glorious One' made a name for himself in NXT as a narcissistic but aggressive heel which eventually earned him a spot on the main roster. Roode was also a heel for the majority of his time prior to NXT, in TNA. Roode is clearly experienced in this role and better suited to it when compared to his current persona.
At the moment, Roode is not much more than a wrestler with a popular entrance. If he is to reach the heights that he achieved in NXT, then WWE could turn him into a Lex Luger style narcissist, obsessing over his own body image and mocking audiences. Roode could even emulate the heel character he played in TNA as one half of Beer Money Inc, as a smash-mouthed, aggressive, beer-drinking heel.
Whether the WWE audience will take to Bobby Roode being a heel is unclear. Although his hugely popular 'glorious' entrance in many ways has worked against him, if he were to drop that theme and make a serious run as a detestable bad guy then it could help push him to new heights.