Yeah these are kind of the only options right - glad the consensus sits on only really these two.
Depends on your criteria - the Nova/NC game was for THE chip so that's a huge factor and someone else pointed out quite correctly that NC had forced the situation with a prayer of their own. I think the fact it was played in front on what 75'000 people slightly warps the perception of that game favorably because the crowd reactions are justifiably insane.
On the other hand that Zaga/UCLA game had a combined 11 more points than that title game (in regular and 32 counting OT) and it's not like either team played bad defense because they didn't. Both teams shot the absolute lights out - especially UCLA which went 0.58/0.47 from the field and 3pt respectively. It was also one overtime period deep already which is something that 2016 title game didn't have.
I'm going to give it to the Gonzaga/UCLA game for this reason. From tip-off to final buzzer I think it was a better game in it's entirety, and also because this was huge for the program and the legacy of Mark Few. Villanova of course had a title and a handful of final 4's by 2016 and NC needs no mention. But this sends Gonzaga to their first ever final 4 and had they not made it this time, it would have been a crushing blow to be undefeated until losing to an 11 seed (albeit a clearly excellent one that was more of a 2-3 seed quality) and missing out on the final 4. A lot was riding on that shot.
No wrong answer though. Both epic games.