I'm not sure there was a bigger one for TV since... or before for that matter.
I put the Youtube of the bigger one in my post! The Moldavian Massacre (1985) had everyone talking for a summer. And, of course, there's Who Killed Laura Palmer (and shot Agent Cooper)? Summer of 90, man. And the first season of Survivor. And the first season of Lost -- WAAAAAALLLLLTTTT!!!!. And when KITT got creamed. And the original V and buildup for Final Battle. The Sopranos finale. Wire-mania.
106 million people watched the MASH finale. 106 million! The most watched moment of television in history.
The Roots miniseries consumed a summer... As did OJ's trail and Iran-Contra, if you count those as TV.
What about Kaufman's stunt?
You and I weren't even close to being born but you can summon up an image of the Beatles on Ed Sullivan, yes?