it's like asking what was the most satisfying sex
All Buckeye victories are pretty orgasmatic, but like sex, having to wait a long time and doing something new seems to make it better, so the Tressel's first W in AA was pretty damn good.
In fact, beating Michigan anytime is like shagging the rich, snotty, school bully's hot girlfriend, shame-ing him into exile for a year and then realizing that the all the other girls in school have come to know just what kind of prodigy you really are..... (sorry to report that it never happened to me)...
Still, I think beating the Canes was even better.
I drove from Dallas to Atlanta (and back) in the two days before the National Championship game. I had to listen to 20 hours of Buckeye-bashing from every idiot across the South (and nationally) who had access to the public airwaves. (In fairness, the sports newscasters in Tuscaloosa predicted an OSU victory...I've liked Alabama much more since).
Hearing people choke on their own words for a month made the victory over Miami really satisfying. I got to gloat to my students (including about 10 football players at a D-1 program in the south) who dissed my Buckeyes all season long. That was very, very satisfying. I smile about it still today.
Thank you Buckeyes!