Patrick Stewart had so many great moments, it's hard to pick just one. So many great ones already stated. But in terms of sheer emotional management, I concur that his dealing with Sarek's emotions in "
Sarek"... I can't help but have tears well up in my eyes, feeling total empathy.
I thought Frakes did a terrific job in "
Frame of Mind." Probably his best acting of the series, where he's mentally manipulated into believing he's incarcerated. So much better than "
Future Imperfect."
"
The Drumhead" isn't one of my favorite episodes, but it's wonderful to see Jean Simmons in action, a major Hollywood star from years past. The "witch hunt" is such a key social manifestation that I think will always require mindfulness to keep it at bay. Look at today. The reversal, where someone declares there's a witch hunt when there is none. The writing was great and Patrick Stewart's delivery so masterful. Poignant words for all time.
"
Unification" parts 1 & 2 finally brought Leonard Nimoy into the series as Spock. I remember waiting so eagerly for the chance that he might. Seeing it realized was so captivating. Nimoy did a fine job.
When James Doohan reprised Scotty in "
Relics," I saw so much of a reflection of TOS. It had its time... "He knows that it's time to stop." Prophetic, as the TOS movies were heading for retirement. Generations came out 2 years later. Doohan was a good actor, but in the TOS movies he didn't get a chance to flex his acting muscle all that much. TNG "
Relics" gave him that chance. Of course, Stewart would upstage him in talent, but I like how Doohan managed himself in the episode. A fitting send off to his Star Trek career.