Drew Brees - made it to a Conference Championship in his sixth season.
Peyton Manning - made it to a Conference Championship in his sixth season.
Dan Marino - NFL MVP, won a Conference Championship, & played in a Super Bowl in his second season.
John Elway - won 2 Conference Championships & made it to 2 Super Bowls in his first 5 seasons.
Jim Kelly - made it to Conference Championship in his fifth season (3rd NFL season).
Non of our post-Aikman QBs should be compared to the guys you listed. They actually did get results that showed their potential. Non of our post-Aikman QBs have gotten anywhere even close to the guys on your list in first 6 seasons comparisons. I like Dak, and he is the guy for now, but he, like Romo, did not get results that compare favorably with your list.