I'm going to preemptively throw out the first four seasons of Babylon 5. Tightly written, well planned and lacking any meaningful presence of techno-babble. The 5th season was such a letdown after I got through the end of 4, which was amazing.

Seasons 2-7 of Stargate SG1. I can't really get more specific than that because I can't really remember, but I do remember that when I did the start-to-finish binge on the DVD box sets about three years back I didn't enjoy Season 1 very much, and it went downhill during 8 and never really recovered. Loving SG1 may just be nostalgia goggles for me since our family used to watch it when it was on TV as a youngin'.