My all-time favorite TNG teaser was for 'The Best of Both Worlds pt1
I love, LOVE, the way Riker's line is modulated for the teaser. Not kidding. I don't know why, I just stuff like that.
I wish they had included the 'countdown' promos. Those are my very earliest memories of TNG, from the summer when I was still familiarizing myself with classic TOS. As I recall the title used to 'explode' onto the screen at the end of each promo (as I think it continued doing until almost halfway through S1 when re-runs started airing -- then somebody went back and inserted the newer '3D wipe' title effect on all of the 'next episode' promos to date).