Also regarding Roman/Cena comps: in-ring, it's close. Cena was booked better throughout his career and even when he was booked against stiffs such as Khali, the writing was good.
Roman was screwed out of a title win at WM31 and spent the rest of the year in dead-end programs against Big Show and Wyatt. The writing was bad yet he still managed to make those matches feel important.
On the other hand, as a draw/mainstream star, Cena still takes it. However, given Roman's football background, he does have some mainstream appeal, but not as much as John. He may get close, but I doubt anyone will reach that level anytime soon.