I voted for last year's play. The excitement it generated was on a higher level. When Kearse won the game last Sunday, it completed a drive that I think most Hawks fans expected to end in a TD. Not to mention, last year's play got Russell Wilson to his first SB. You could argue that Seattle won their first SB that night psychologically. The fact that it came over the 49ers is huge too.
I think both these plays are over-rated anyway. Seattle was an overwhelming favorite to win the game when the ball was snapped on the tip play. SF had less than 30 seconds and needed a TD with a QB who was miserable in the red zone for his entire career against Seattle. When Kaepernick gets close to the end zone he basically morphs into Dan McGwire. The 49ers statistical win probability at that point in the game was less than 25%, but their actual probability was probably closer to 5% given Kaep's history. I felt completely safe during that last drive.
With the Kearse catch vs. GB, it was basically the least amazing component of Seattle's insane comeback.
In both cases, it's not really the play, but the game that proceded it that was so awesome. But we have to pick a moment, don't we? And I guess the game winner is the logical choice. For me though, It's the 4th in 7 in the 2013 NFCCG, and the Matthews onside kick recovery in the 2014 version.