If there is an argument for TAS being the best Star Trek series, I am not the one to make it. I was pretty much kidding when I posted that. I DO really like TAS, however...
I have actually only ever seen maybe four or five episodes of TAS. I remember watching it a few times before Robotech on the Sci-Fi channel back when I was a little kid... and totally loving it. I watched an episode a few years ago, and really liked it. The music, the voices, the sound effects, that crazy alien helmsman... it's awesome.
This may sound cheesy, but I am actually deliberately NOT watching all of TAS... so that for me there will always be a frontier of unwatched Star Trek. Where Kirk, Spock, Bones, and Scotty are on one of NCC-1701's five-year missions, having some new adventure.
I'm sure I'll break down someday, when I can pay some reasonable fee to instantly download high quality versions to my holocube implant, and actually watch them. But until then... Trek on, USS Enterprise!
(that's pretty nerdy, eh?)