I think I'll have tosay the Next Gen as it was the one that really got over with the masses. The original didn't date too well DS9 is plain boring, never watched Voyager. Like Enterprise but STNG was better.
Probably the original series, not a huge trekky fan but the original series had so many great episodes and memorable moments,none of the others were all that good really.
ST:TNG all the way for me. I find the original series a bit silly! I reckon DS9 suffered from a lack of movement with it being set on a station, which probably brought about the introduction of The Delta Flyer. I really enjoyed Voyager as I thought it was a breath of fresh air with a whole new idea, and it would come second in my ratings. I never really got into Enterprise, I find that one of the main 'believability' issues in Star Trek is that they tend to use (virtually) unknown actors, so to cast Scott Bakula as Archer was a mistake in my eyes. Make it so!
Not really got much of an opinion on this, I've seen a few episodes of them all and they were all OK, but I guess the one that stuck in my memory the most was the next generation so I voted for that.
Also I've been told to point out to DoctorOfDesire that the Delta Flyer was in Voyager and not Deep Space 9.
I had to go for TNG. I've probably seen all the series through at least twice with the exception of Enterprise... which was largely tripe until the 4th series so I largely ignore it. It was hard to pick between the original and TNG, however TNG edged it as that was the one that I first started watching when I was but a small child and it was novel having an English captain even if he was pretending to play a frog. Also for me DS9 came a close third, as it was a bit different and kind of edged away from the more utopian lovey dovey society as shown in TNG.