The back story on the Newhart finale is great. They had to hide Suzanne Pleschett in a trailer so no one would see her until they taped the scene. They were able to duplicate their old bedroom decor.
If you know the mind of Larry David, Seinfeld's ending was spot-on. Certain things maybe they could have handled better, but I'm so glad they didn't conform to typical sitcom expectations. Nothing about that show was typical.
Now contrast that with the predictable schlock of Friends...
I'm also in the boat of saying The Sopranos leaving the ending open to interpretation was fantastic.