#1. Cesaro
Cesaro will go down as one of the most underutilized Superstars in the last five years. 2014-15 would have been his ideal time to shine, but he was never viewed as a top star by the WWE top brass.
Vince McMahon himself went out of his way to say that he felt Cesaro wasn't charismatic enough. When given the opportunity, The Swiss Superman has mesmerized audiences and gotten over in no time.
He isn't the worst talker either, though his lack of character has been detrimental to him overall. Still, his WWE career will be looked at as an accomplished one and there's no shame in having been an upper midcarder.
However, the fact that he's a physical specimen and sometimes superhuman in the ring could have gotten him over and made him one of the most exciting stars of the Attitude Era. In-ring content didn't matter as much, but when a Superstar is that good, it's too hard to not take notice of it. Cesaro could have possibly thrived in the Attitude Era.