Love it...
Voyager: Standed StarShip 75,000 LY's from the Federation, lost in totally unknown space, never knowning what around the next nebula. Well casted, love the Intrepid Class Star-Ship design...
DS-9: Fell in love with this series in it's original run. Totally cool concept, Cardissian Space Station that for some reason they did not self destruct.
A true melting pot of the Federation. A planet that was just coming out of almost 50 years of occupation, a worm hole leading to a very remote part of the GQ. This series had it all, humor, tragidy, spirtiual, greed, they really had it all. The first Trek that did not have to go to the stars, but it did not matter...
TNG: The one that brought Trek back to TV after almost 25 years. Loved the Enterpise, Pickard, Riker, Data, Worf, Geordi, Dr's Chrusher and Pelouski, Deanna and yes even Westley (the butt of many a good joke)
Introuduced us to Holodecks, Replicators, 10 Forward. How could you not love it...
TOS: As Gene Roddenberry put it "Wagon Train to the Stars" Kirk, Spock, McCoy, Scotty, Chekov, Uhurha, Sulu, Rand. For a kid just growing up in the mid to late 60's I could not wait until the next episode to see what new adventures lay in store for our heros. It brought space and space travel much closer, seeing the moon landing just a couple of years later sealed the deal, we were going to the stars. Star Trek and Apollo 11... could it get any better
Sorry to say that I never watch much of Enterprise, so I cannot comment on this series, I do plan on getting the DVD's soon...
In a way, this was a unfair question, for all the series did mean something different to me in they all came around at different times in my life. Not so much the latter DS-9, and Voyager, but TOS and TNG. They are all so different, yet, they are in some ways very simular. We can go back and forth about which series was the best. I prefer to say that Star Trek Rules !!!!!!!