I'd never claim it as "most awesome" but Season 1 (especially if seen on DVD, i.e. over two RT days
was pretty stunning. Looking back, it doesn't bear a moment's rational examination but at the time it was an exciting journey. I'd also mention the shocking event near the start of Season 5. That was a jaw-dropping moment.
Not, perhaps, awesome but a South to 24's North Pole is West Wing. The first four seasons were consistently well written, willing to go into issues and it was funny as well.
Firefly (great because it never had the opportunity to outstay its welcome).
BtVS/Angel had their moments.
Not on my awesome list but surely worthy of mention is Babylon 5.
And, of course, Stargate SG-1. Not just awesome but 214 episodes of awesome.
A lot of older series don't compare well (partly because cheap special effects look so much better these days). It's probably not fair to compare them.
Edit: Forgot - Farscape. 1st two seasons were amazing.