When I tell people that I liked Trek, I essentially mean TOS and DS9.
TOS was the correct Trek for the 60s -- brash, hopeful, forward looking, but with moral quandaries that had to be faced, the notion that even with superior technology we still carry problems within us. The human factor, even when in alien guise was both the blessing and the curse of the universe. Above all, there was hope.
DS9 was correct for its time -- still hopeful, but a bit more wary. Humankind, even in the form of the generally benevolent Federation, was far from perfect. There were cracks in the foundation, mistrust, and even mistakes. Yet for all this, and perhaps even because of this, it was still a very hopeful series. Even in the face of shifting alliances, even in the face of secrets hidden within an otherwise judicious government, even in the face of religious zealotry, there was the hope that things could and would improve, that the human spirit (again, even when in alien guise) would rise to the occasion.
TNG was a bit too clean, too PC for my tastes, though it had some excellent episodes (none of which was a two-parter). VOY lost my interest pretty much from the first episode because it blew one of the most fascinating ideas of its premise immediately -- how do you hold such a disparate crew together with two differing visions of how life should be led and who should command (Maquis v. Federation). Enterprise I didn't see enough to really critique, but I was saddened with the couple episodes I did see for the way they messed with the timeline.
In the end, however, it all comes down to the moral quandry episodes for me. Often in TOS a single decision and point of view was reached, and this was fine. In DS9 there were often many shaded points of view, each valid under a particular set of circumstances, and this again was fine.
And in the end, here is to Ben Sisko, the captain stuck in the most difficult position possible (Federation/Bajoran, Starfleet/Civilian, Human/Emmissary, etc.), who carried it all off with panache!
