Well.. I haven't played Season 3 yet so I can't completely judge on that factor alone and by itself, so.. I'll choose everything up to Season 2. They're not in any specific order, so I'll just list the ones that really weren't my favorites.
1. Moai Better Blues
2. Abe Lincoln Must Die!
3. Culture Shock!
as mathman77 said, Culture Shock! is the pilot, so really it's best to cut some slack. I actually kinda liked it more first playing it, but now it must be one of the few that's kinda meh to me.
..when I kick it.