Mind you this is off the top of my head and I definitely think I'm forgetting a lot of my top British series and older series.
1. Friday Night Lights
2. The Wire
3. Frontline
4. ER
5. Homicide: Life on the Street
6. Community
7. The Twilight Zone
8. I Love Lucy
9. Arrested Development
10. Futurama
11. Game of Thrones (*, obviously could be premature if its quality falls off a cliff later on)
12. Six Feet Under
13. Spaced
14. Rubicon (RIP)
15. The Muppet Show
16. The Simpsons (penalized for damaging its reputation for the past 12+ years)
17. Luck (RIP)
18. The X-Files
19. Homeland (*, obviously could be premature if its quality falls off a cliff later on)
20. Deadwood
21. Spooks (MI-5)
22. Lost
23. Justified (on the rise)
24. Scrubs
25. Treme (*, obviously could be premature if its quality falls off a cliff later on, or it could rise)
26. Veronica Mars
27. 24 (S1-3 rank it a lot higher, say top 20)
28. Damages
29. Breaking Bad (I'm the contrarian that doesn't laud AMC outside of Rubicon, because their shows lack relatable characters, but the gutwrenching ethical dilemmas of this show rank it on my list)
30. Brotherhood (most underrated award)
31. MASH
32. Carnivale
33. Terriers (RIP(
34. The Office (UK)
35. Batman: The Animated Series
36. Life on Mars (UK)
37. Law & Order
38. Freaks & Geeks
39. Hey Arnold!
40. Pushing Daisies
41. The Hour (*, obviously could be premature if its quality falls off a cliff later on)
42. In Treatment
43. Twin Peaks
44. Extras
45. My So-Called Life
46. Luther (could rise with subsequent episodes)
47. 30 Rock
48. Rome (could have been higher, but not getting a real finish hurts it)
49. Kings
50. Heroes (by virtue of season 1 being one of the most ambitious slow burn developments in TV history, unfortunately for it, the rest of the seasons exist).
There's obvious stuff people want included on top tv lists that I just don't enjoy watching, like Mad Men & The Sopranos, I'm not pissing on their quality, they're just unenjoyable to me.