I still can't figure out how so many people have been brainwashed into thinking "No soup for you" was funny? It was the same joke over and over and over. I only watched about a dozen seinfeld episodes and never found one of them to be funny enough to rate the show as highly as it has been rated.
(But I agree it was worth watching)
for "of All-Time", I think the award would have to go to something like Lucy or Mash... something else that survived the test of time (like Seinfeld did). Judged by today's standards, even the Brady Bunch looks like a stupid show, but in its time, it was well watched.
I however prefer Simpsons over Seinfeld any day.... and couldn't stand the show Friends... too soap opera-ish.
And, I agree with those who think Cheers was an awesome show. It's too hard for me to decide on #1, but it wasn't Seinfeld.