I have a sneaking affection for Voyager. I think it's better than early Next Generation (when I saw the first season of that again, I thought "Oh, yes, that's why I gave up on it when they originally showed it.") Obviously TNG became much better, once it hit its stride (Raiker growing a beard and being written as a proper character struck me as a key moment), but I like Voyager precisely because of its flaws. I look at late TNG and think "Yes, they were trying to do that, and they did it very well" (and on those grounds, I'd probably accept it as "definitive Trek"). But I look at Voyager and start thinking about how I'd fix it. With TNG there's nothing to fix, so I admire the ensemble acting and pass on.

For the purposes of this poll, of course, I am taking "definitive Trek" to mean "the single series which justifies the existence of the whole of the rest of Trek, before and after, though I'm not very bothered whether I see any of the others again".