You need to look at context. Rodgers is a lot higher than Romo's, having a 103.8 QB rating. As for Brady, since 2007, outside of his 2013 season, Brady has a higher QB rating than Romo. 2007 is when Brady transcended into a legendary QB. Drew Brees since 2009 has 6 seasons with a 100+ rating, while Manning had 6+ seasons with a 100+ rating as well. Romo had two.
Yes, Romo was consistently great QB, but we are talking legendary. The guys we are talking about are players who are consistently great and at their peak were QBs that played at levels we've never seen before.
Romo is with the Rivers type QBs. As I said, there is nothing wrong with this. Great players who had a couple elite seasons, but they never reached legendary status.