I kind of lost interest in the series towards the end of TNG, and never really got into any of the follow-ons. When I go back to watch the original series again, I sometimes feel as if it's not quite as ground-breaking as it seemed back then, but I suppose that's true of a lot of older TV and movies.
I guess I associate more with characters, and was drawn to Spock on the original and Data on TNG. In some ways, they're kind of plays on the same basic premise, but I thought they were able to explore things a little more deeply and broadly with Data, so he's probably my very favorite (**looks at my forum name. "duh!"**).
That said, I do love this idea about the original where Kirk, Spock and McCoy represented three aspects of one's internal dialogue, which were separated in the show to have the dialogue expressed out loud instead. Now I have to look at every significant work relationship I've had, and try to find the two closest people to me at the time and assign a Kirk, Spock or McCoy tag on each of us. (Hint: I'm always either McCoy or Spock). I think in the end, the McCoy character got overshadowed by the Kirk/Spock bromance (romance?), and sadly became a kind of third whiny wheel. Sigh.
Erin