Oh, didn't see that. Sorry OP. ^^
In my defense, it's super bright outside and it makes reading on my phone a lot trickier.
For TNG - the most important ones for me have already been mentioned here.
Not necessarily my favorite TNG episodes exactly but some of the best demonstrations of the philosophy of Star Trek (among the ones that haven't already been mentioned at this point):
The Quality of Life
Half a Life
I'll second Darmok, The Measure of a Man, and Drumhead.
Oh and, anyone from Paramount* thinking of a new Star Trek series should read these comments and watch every episode mentioned. THIS is what makes Star Trek great, not any of its action or temporal timelines.