You forgot Andrew Luck doesn't play well in the playoffs.

.
He makes Manning look like Montana in a Super Bowl.
Based on a 6 game sample size, the first three years of his career.
Look at Montana's first 6 playoff games.
Luck: 1829 yards, 9 TD, 12 INT. 25 years old at time of game #6.
Montana: 1604 yards, 13 TD, 11 INT. 28 years old at the time of game #6.
Took him until year 3 to even get to the postseason.
Montana was 3 years older and his stats aren't significantly better through postseason game #6.
Even if you want to say his stats are better, they are nothing special.