This is a two play race for me. The Edelman catch was excellent, but it was 1st and 10 with plenty of time left, in the 5th of 6 super bowl wins. The catch was ultimately a 5-10% swing in win expectancy, which falls short. Real good play but without much effort I could come up with a dozen plays that had more meaning.
The snow kick was even more amazing but the stakes were just so much lower - like the Roberts steal, most of the importance of this play depends on what comes later. A team that has been to 13 conference title games and 9 super bowls in the last 18 years cannot have their greatest play be in the divisional round, sorry.
It's between the SB 36 game winner, and the Butler pick. For me, it's the Butler pick. It had a greater swing in win expectancy (per an article a few years ago by PFR, this was the third greatest swing in SB history, behind the Norwood miss and Burress' TD in SB 42), and it's easy to forget now, but at that point the Pats were 9 years removed from their last title and had not totally separated themselves from other dynasties. Not as meaningful as the SB 36 kick that started the whole thing, but the pick was a better play, definitely a greater shock and jumpstarted the second half of the Pats' dynasty, which cemented Brady/Belichick as the respective GOATs. Brady was 37 and about to lose his third straight SB, after two weeks of deflategate nonsense. For me, it's the Butler pick.
*edit - a play that should be considered that I haven't seen yet is the Law pick 6.