There are so many ways to answer this question, depending on one's definition of "best" or the criteria one chooses to employ. For more than five decades, I regarded the 1971 Nebraska-Oklahoma game as the "best," i.e., most entertaining game I personally watched, especially since it was a matchup between the numbers one- and two-ranked teams in the country. That position, however, has now been usurped by the 2022 Tennessee-Alabama game.
However, if one defines "best," in this context as most dominating performance, yes, excellent arguments can be made for victories over LSU, Kentucky and, despite our historical contempt for them as an opponent, Vanderbilt. We slaughtered the Commode flushers 56-0 on their home field when they were playing for a bowl bid. It is difficult to shut anybody out these days and, arguably, the only victory over Vandy that was more rewarding was the thermonuclear devastation that we unleashed upon them in 1994, when the final score was 65-0. Coach Cafego would have been very proud of our lads on that day.