Is this the biggest regular season game in Giants history? You could certainly make that case. The Giants have played in only a handful of all-or-nothing regular-season games at the end of the season, do-or-die games that had nothing to do with outside events. In other words, take out the 1988 game against the Jets because there was still a backdoor for the Giants to get into the playoffs.
This, by the way, is believed to be the first time in franchise history that the Giants are going head-to-head in a winner-take-all game where the loser's season ends.
Some others that came close:
In 1943 the Giants had to beat the Redskins twice in the final two weeks of the regular season to force an Eastern Division Playoff Game. They did, by the scores of 14-10 and 31-7, to finish in a tie for first place with the Skins. The following week they played for a third consecutive game. This time the Redskins won, 28-0.
In 1958 the Giants had to beat the Browns, once again to force a playoff for the Eastern Division title. They won 13-10 to force the playoff, then beat the Browns 10-0 the following week. That win advanced them to the NFL Championship Game where they lost to the Colts in the Greatest Game Ever Played.
In 1970 the Giants needed to beat the Rams in the regular season finale to get into the playoffs. The Giants wound up losing, 31-3, and finished in second place in the NFC East with a 9-5 record. The Rams won, but they didn’t make the playoffs that year either.