I will just list the ones where, to my knowledge, I have seen every single episode at least once. This list alone is embarrassing enough. Hell, I am watching an episode of #43 right now....

50. Quantum Leap
47. Star Trek: Deep Space Nine
46. Sex & The City
43. Star Trek
42. Only Fools and Horses
39. Monty Python's Flying Circus
38. Curb Your Enthusiasm
37. Star Trek: The Next Generation
36. Father Ted
34. Frasier
28. Fawlty Towers
27. Six Feet Under
26. Red Dwarf
25. Futurama
24. Twin Peaks
23. The Office UK
20. Blackadder
17. South Park
16. Doctor Who (new version)
12. Family Guy
11. Seinfeld
09. The X-Files
01. The Simpsons