I'm going to assume we're talking about episodes made at the peak of the original run - I'm not interested in a reunion or what could be late era stuff where things were less good.
Friday Night Lights - loved this show back in the day, would have loved another season before coach Taylor headed off to East Dillon.
Fawlty Towers - so few episodes, such a long shadow. There should have been more!
Frasier - still stands up today, would love to see some never seen before episodes.
Breaking Bad - not sure how this would work, but just more story from sometime around S3.
I'm not sure what my 5th would be.