Seinfeld is pretty much a about selfish people and how they don't go by th rules society has imposed upon us. Its about doing what is best for us and forget what people may say. Jerry and George date different girls every episode, why? Because they are shallow individuals and its funny to ser people actually being as superficial as they can. Elaine is the same way, screening candidates before using a sponge. If you watch the final episode you can see all the people they have wrongred during the show's run and it finally bit them in the ass. I wish I could be that selfish and just look after myself and seeing them doing that is what makes it funny.
Also the humor is not just your regular sitcom humor, it is smart and if you love that kind of humor you just know and find yourself using it all the time and has become part of our every day vocabulary "double dip", "festivus", "serenity now", they are just too many to mention. I LOVE SEINFELD. If you don't get what makes it funny, then nobody can explain it to you and you are seriously missing out.