There was so much great stuff in 97-98 that I was completely worn out as a fan by 1999. Pretty much everything Austin touched turned to gold, but then there's stuff like Waltman's return the night after WM14 or Foley quitting the WWF, which both felt game changing at the time but seem kinda forgotten these days.
The Rock vs. Mankind I Quit Match or Triple H vs. Cactus Jack Street Fight. Mainly because we'll never see anything like them again. You could theoretically do the entire Austin angle these days without the swearing. I never got the extreme popularity of Austin but then again I started watching in early'98 when the initial Austin/McMahon feud was seguing into the whole Corporate Ministry angle.