re: Does Manning's legacy survive this?

This definitely drops him out of the GOAT consideration. I can't look past his faults in big games (particularly Super Bowl). It dates back to his days at Tennessee. He just struggled to win the majority of the big games.

His Super Bowl stats:

Indianapolis Colts vs. Chicago Bears:
25/38 247 yards 1 touchdown 1 interception
Colts - 29 Bears - 17

Indianapolis Colts vs. New Orleans Saints
31/45 333 yards 1 touchdown 1 interception for touchdown
Saints - 31 Colts - 17

Denver Broncos vs. Seattle Seahawks
34/49 280 yards 1 touchdown 2 interceptions [1 being for a touchdown] and 1 fumble. This game could have been a lot worse as well. Seattle was really backing off and playing prevent towards the end.

I can't look past these. His regular season numbers are unreal. Yet, if he was in the NFC playing against Arizona, San Francisco, Seattle, St. Louis's defensive line and such, these numbers would not be as high.

Bottom line, he's a great quarterback with a Super Bowl victory. GOAT? No. He has too much going against his record.