I think a big part of what "represents" WWE is the idea of pro wrestling as a three-ring circus, with a bunch of different things going on at the same time to appeal to as broad an audience as possible, so I'm not sure one match can do the job. If I'm allowed to package two together, however, I'd go with Savage/Steamboat and Hogan/Andre from WM3.
Two matches, same show, one with no redeeming value whatsoever as a wrestling match but a second-to-none spectacle; the other an athletic clinic that's still a classic nearly 30 years later. One put eyes on the company; the other made them glad they were there.
Golden age - Hulk Vs Andre
New stars -.... wasn't watching
Attitude era - Mankind vs Undertaker (HIAC)
Ruthless Agression...... Wasn't watching
PG - Only been watching a year.. Shield Vs Wyatts. Well that match says 2014