I am not sure I'd show "All Good Things..." to a first-time viewer.
From my personal experience 'All Good Things...' would be perfect, in the late 90s it was the only availanbe episode to buy on VHS, I got it and loved it and still do.
AGT also introduces Tasha if one doesn't want to go to season 1 episodes. Soon after that 'Legacy' would be a good view, it has Tasha's sister.
If I were to introduce someone to TNG, these would be the episodes.... maybe.
- All Good Things...' in one or two parts, originally it was hour and a half..
and then continue with great ones from season 3 when the show really gets going, something like
- The Bonding
- Who Watches The watchers
- The Defector
- Sins of the Father
- Evolution
- The Offspring
- Yesterday's Enterprise
Before going into the final episode of season 3 you should check out season 2 episode 'Q Who', first contact with the Borg.
And then into season 4.
But if you want to pick the best of the best pick the episodes listed above and then....
- Data's Day
- Clues
- Reunion
- Night Terrors
- The Nth Degree
- Redemption 1 & 2
- I Borg
Something like that.
That list might be missing more than a few but you'll find them.
