I grew up watching Seinfeld.
I think that the claim that it's the greatest sitcom of all time is a bit over-the-top. It's more of that it's an American icon as far as sitcoms go. It was a random, off-the-wall idea that had never been tried before. It combined many, many plots all resolving in one at the end. It avoided all the cheesy drama that sitcoms always pulled in at the time. It really was the most original thing ever made when it came out.
However, with new American shows like Arrested Development, 30 Rock, Andy Barker P.I., Scrubs, (would say The Office, but that's yours)...Seinfeld lost a lot of it's originality.
Good show for anyone into writing comedy to watch.