The original, hands-down. Despite some ridiculous episodes (Spock's Brain being a prime example), it was the dynamic of the relationships between Kirk, Spock and McCoy that made it so immensely enjoyable to watch. Plus, the genius of Roddenberry to put mixed races and nationalities on the board of the ship (including putting a Russian and an African-American woman on the bridge in the middle of the Cold War and at the flashpoint of the Civil Rights movement), not to mention foreshadowing desktop computers, floppy disks and a whole host of other technological advances (though I'm still waiting for my transporter!). I have happy memories of discussing issues like the merits of the Prime Directive, changing history via time travel, etc., based upon episodes of the original series and I enjoy watching them to this very day.

The original series. What else is there?

Original. Hands down.

The original and Deep Space Nine. The original for its messaging and DS9 becuase it was darker and edgier.

Deep Space 9.

Sorry my friend; I am old school TREK - but I never choose favorites!

NextGen

DS9, hands down.

DS9,loved it

The one with Patrick Stewart

The original. It touched on "taboos" and diversity in the early sixties long before our society was ready to accept it. Even though there were only three season it has endured.

Next Gen is where I hope the future lives with many excellent stories! The original series and movies were my gate way. Voyager was ok but I watched it irregularly. I missed Deep Space Nine, Enterprise, and Dicovery.

TNG has always been my favorite

DS9, even if it was a rip-off of Babylon 5.

TNG.

Well, I'm a sucker for all of them, but TOS captures Roddenberry's 23 century secular vision better than any other series. I liked TNG but they should have thrown Wesley Crusher out the airlock. Absolutely love the character of Q. The greatest and most misunderstood character in the ST mythology. Voyager was sooooo politically correct it made my teeth ache. Love the episodes with Q in Voyager, though. The episode "Death Wish" has a number of huge philosophical implications about the Q Continuum. The space station series didn't do much for me, though others loved it. I really liked Enterprise, though it was fashioned in a post 9/11 environment and misty eyed Trekkers didn't care for it. The new one, Discovery, I'm holding judgement and see where it goes. It's a mess in terms of consistency with tv and movies, but there it is. I do feel Roddenberry's secular vision is just about gone, however. I suppose it reflects the age we live in, sadly.

DS9. Dark and yet funny.

The original tv series.

I like the darker feel of DS9.

Red Dwarf, for sure.

I would have to go with DS9.
TNG a close second. Very close.
I never really watched the Original, it gets silly.

For years it was TOS but I totally love TNG and Patrick Stewart is an awesome actor.

Next Generation.

TNG, followed by Enterprise. Of course, I grew up on TOS, and will always like it. I did like Voyager and DS9.... but I got into DS9 much later and haven't seen a lot of it before Worf arrived. As for Discovery, I've seen only the first hour, so I can't say. I'll reserve judgement on that one.

The next generation by far they still air it on BBC in the afternoons. Great stories with life meanings if you look deeper into it.