Is it really Roman though?
He only really came into the "Great" status over these last 4 years, while he had to counter out eight years of a mostly underwhelming main WWE Roster run, mostly due to booking. You could see some glimpses here and there during that, but he was far from being that complete Main Event guy he is now. The only thing he always had over Zack is the Superstar look, but other than that ZSJ been going strong(er) for longer than Roman. On the mic, in the Ring and when it comes to character work.
And don't get me wrong, I always liked Roman. Even during his horrible babyface pushes.