Right in those cases I am talking about the recent remakes. I didn't look into the lengths... but I think the majority of them are hour and a half ones. Which either way... I would never get them all in!
I just went through my TV Show collection... here is some series that I think are horror related enough that I can watch any episode of and include in my marathon...
1. American Gothic: Complete Series
2. Angel: Seasons 1-5 (Complete)
3. Are You Afraid of the Dark: Freaky Favorites
4. Beyond Reality: Season 1
5. Blood Ties: Season 1
6. Buffy the Vampire Slayer: Seasons 1-7 (Complete)
7. Dracula: The Series
8. Eerie Indiana (3 Episodes)
9. Fear, Itself: The Complete Series
10. Forever Knight: Seasons 1-3 (Complete)
11. Friday the 13th: The Series: Seasons 1-2
12. Ghost Whisperer: Seasons 1-3
13. Haunted: The Complete Series
14. A Haunting: Seasons 1-4 (Complete)
15. The Hunger: Season 1
16. Kindred: The Embrace: The Complete Series
17. Kingdom Hospital: The Entire Series
18. Kolchak: The Night Stalker: Complete Series
19. Masters of Horror: Compete Series
20. Miracles: Complete Series
21. Monster Squad: Complete Series
22. Moonlight: Complete Series
23. Night Stalker: Complete Series
24. The Ray Bradbury Theater: Complete Series
25. Supernatural: Seasons 1-4
26. Tales from the Crypt: Seasons 1-7 (Complete)
27. Tales from the Darkside: Seasons 1-2