1999 is the greatest TV year in wrestling history IMO, the crowds were on fire, Rock and Austin were on fire, WWF's popularity, ratings, buyrates, awesome storylines and memorable matches. 2000 was better in terms of wrestling, storylines were great too, the most successful year for any wrestling company ever, plenty of memorable programs, fresh matches and just a mega hot program with tremendous TV and PPV month after month. The Rock/Mankind/Austin/Vince/Shane/Show angle in 99 was one of the best programs of all time. This period in the start of 99 is probably my favorite time in wrestling history. So many great things happening all at once, business is huge, mainstream attention all over the product, wrestlers all over TV shows, amazing time. Same with 2000 if not more BTW because nobody in wrestling history had a better, bigger or more successful year than The Rock 2000, that's when the industry peaked forever.
For me it's 2001, I just loved it to be honest, as a kid growing up the whole InVasion angle and the possability of the WWF going out of business was a huge thing for me. Plus every week runins or changes/jumping ship was keeping me on the edge of my seat, not to mention some of the greatest weekly matches of all time. 2000 isn't far behind though.