TNG #1 in my book, man (although I wasn't a fan of Star Trek or sci-fi in general at the time - I was like 8 at the time).
Honorable mentions also go to DS9 (loved that Dominion War), Voyager (certain plots and characters, but barely made it in my book), the X-Files (pre-8th season), the X-Files spinoff, the Lone Gunmen (I love those conspiracy-type shows, and the guys were great). I didn't get into much else, and I only got basic cable here, so I don't get the reruns of the other shows (just Voyager every weekday at 4 p.m. and the X-Files every saturday on NBC).