"The Measure of a Man", "The High Ground", "Legacy", and "Unification" instantly come to mind for me.
As does one other -- it's also Bender Robot's favorite episode of TNG, which he names enthusiastically here:
Or for 10 hours here:
And now, a brief synopsis adumbrating the reasons:
"Measure" - more and more plot holes over Data's alleged sentience and other correlations were off-putting. At least Riker didn't know of the off switch... oh wait, he did but nobody else made a point of it as rebuttal.
"High Ground" - it's just about a guy who has the hots for Crusher and I must say, the video below sorta nails it... even if the
show is being mindful of kids at the time, hence how Wesley was talked down to (then again, kids loved TOS and less of that patronizing took place...) Ansada faction uses weapons that were recycled from the 1985 "V" series, oops, the surrounding plot doesn't de-distract from that distraction, something most season 1 stories managed to do despite other obvious prop reuses like the octagonal bronze container things.
"Remember Me" - works well for its emotional ambiance, almost like Twilight Zone, but doesn't hold up as there isn't enough plot meat, other than "Hi Wes, it's me the mystery weirdo cuz we have nothing else to do but dig up old characters. But you're lucky, Riker gets to think Minuet isn't real in a later episode where he sees through very quickly he's not into being in a nuclear family!" (yeah, "Future Imperfect" is another one in this list too... and wouldn't be if it really was a Romulan ploy...)
"Legacy" - a rewatch revealed way too many plot holes and conveniences; even TOS would blush in envy
"Unification" I thought was okay at the time, but Spock is underused and I loathed even more how badly Sela was treated considering the setup from season 4's finale. (My first instinct at the time was that she would return... but during season 6 I did a rewatch, and another one when the blu-ray came out. )