I had to stop watching a few episodes in. No show so bad and "off" could possibly turn around and make it real and good, I thought. Then I looked in on it partly way through s2, "Pen Pals", and there, the staff was having a conversation about the Prime Directive that actually sounded intelligent. That was a surprise. All the characters had seemed like very tall children in uniforms before this, speaking and thinking simply just to move the simple plot along.
So then I saw "Q Who" (still my favorite) and I had to watch, from then on. Tracy Torme has said that Next Gen peaked in quality at the end of season one. This seems ridiculous at first, but as I went back and saw the ep's I'd missed, very late s1 really did have more to it than the rest of s1, a sort of edge along with the awkwardness, and a sense of weird, incomprehensible danger lurking just offscreen.
Encounter at Farpoint was the only one I liked at all, back then. The idea and visual and message of the ship/starbase was very old-Trek, stronger emotionally than NG became later. Really solid ep's though? "Where No One Has Gone Before", maybe. If not that, skip ahead to late s1, the final few. I'm not completely comfortable with NG until s2 though... another possible "first great one " would be Elementary Dear Data".
One problem is that good stuff is scattered all over, amongst the otherwise bad stories, as well as the good. One scene or even one line can legitimize an ep for me and make it crucial.