Comedy is generational. My grandparents thought Bob Hope, Jack Benny and Arthur Godfrey were the funniest guys around. The only comic they liked that seems even a bit funny to me is Will Rogers, and of course, most of his political topics are beyond dated.
Seinfeld is not as funny to college kids because they are a newer generation. Some of them are probably more than a bit tired of Seinfeld, and it is not his fault. They run his shows in syndication, over and over and over, just as they did Gilligan;s Island, I Dream of Jeannie and I Love Lucy. Few jokes are funny the seventh time around.
Comedy in the US is getting more international, with East Indians, South Africans, Iranians and Chinese getting a laugh at the differences between the culture of their parents and the American culture they grew up in.
Seinfeld is to be commended for ending his series before it "jumped the shark" and became a cliche. He has more money than he ever could spend on any sort of a normal life.