in terms of some of the shows mentioned, Seinfeld is a classic. Hands down. Curb is good stuff, but I prefer Seinfeld.
X-Files solidified the "story arc tv show" concept that pretty much every show has followed since. the arc episode/stand-alone/stand-alone/arc episode format. There wouldn't be your Buffys, Angel, Lost, Smallville, etc. if the X-Files hadn't blown up around seasons 2-3-4
Firefly is definitely among the best. Possibly THE best fourteen episodes of network TV. ever.
and no love for dollhouse? echo? fine fine Whiskey?
shameful.