Code of Honor
You forgot Shades of Gray!
But seriously, it's a bit hard to recommend the perfect episode without knowing a bit about this person and their background. That said, here's a few that I think would be a good introduction to TNG:
The Inner Light
If I had to pick one out of those... maybe Hollow Pursuits? Although the Inner Light is great too. Depends. If they want a serious drama, go for Inner Light, if they're into more light-hearted stuff, Hollow Pursuits.