I've always found Seinfeld to be a hit and miss show. The first three series struggle to find their ground and the fourth series, despite containing some of the most memorable episodes such as The Outing and The Contest, also contains some of the worst, such as The Airport and The Trip. I think the series really found its ground in Series 6 and 7. Both those years have a consistent quality and contain the best examples of Seinfeld's uniquely plotted writing style. Because of this, Series 8 is a bit of a let down. Maybe it's because Larry David left, but the show seems less realistic and more over the top than ever before.
The saving grace of post Series 7 Seinfeld is, without a doubt, The Betrayal. Starting with the final chronological moment in the story and working its way backwards to the beginning of the story (and further), The Betrayal is unlike any other episode of a comedy show in history. It helps that it is also very funny. Although this style may seem slightly convoluted at first, it makes the episode a joy to rewatch as the viewer can make more sense of the reverse threads.
I implore anyone who wants to see something genuinely original or who is interested in writing to watch this superb episode.