Aikman was overrated only to those who are into stats. He didn't have big numbers because the offense and team he played for didn't require him to have big numbers. Other than the numbers he had HOF written all over his career. He had great accuracy, leadership and came up big in the playoffs and SB. He outgunned 3 future FIRST BALLOT HOF QBs in the playoffs and SB that resulted in a Cowboys dynasty that dominated the 90s. He was 7-1 vs Favre, Young and Kelly during the postseason.
As for Romo, I don't know where you get that he's been overrated. Most Cowboy FANS over the years think he's been underrated due to his big numbers and career passer rating. The QB rankings that have been posted on the board over the years have caused many to complain that he hasn't been ranked high enough. A majority of the experts over the years have seldom thought of Romo as an elite top 5 QB. The QBs they've ranked ahead of Romo all have better playoff records and at least one ring.