I'm not big on the original series. The good intentions of the whole idea is outweighed by the total failure to realise them plus it's just kind of hard to stay interested in TV storytelling that primitive, especially when alot of the episodes are just shit, anyway. I don't hate it, but I'm definitely not an original series guy.
Did you know that the original pilot of the original series had a female first officer? The network told Roddenberry to fuck off with that thought, and they tried to get Uhura off the bridge as well but he wouldn't budge on that one apparently. The show is still crazily sexist, obviously, but seeing that he tried to put a woman as the No.2 made me like the guy a little more.
My favourite is TNG. I like DS9 quite alot as well, and I've never watched Voyager or Enterprise very much, just a couple episodes if it was late night and I was bored anyway.