I was a bit fatigued by TNG, but I'd got used to its slow, thoughtful pace, spelt out decision making, and happy endings.
Although I think everybody likes a happy ending, I don't think they're the reason for TNG's success, or lots of cheesy shows throughout history would have been bigger successes with just that.
But I wonder if the Observation Lounge scenes on TNG weren't part of its success. This is science-fiction after all, and isn't the part that makes it really interesting the figuring out of new things? I think part of TNG's success was its procedural aspect. Law & Order was about law, CSI about forensics, ER about medicine, TNG about starshiping. And they didn't just glass planet surfaces to clear their problems; they figured things out...were that our politics today were so.
Some of the most interesting scenes in "In the Pale Moonlight" were the conversations. Sisko and Dax roleplaying about what the Romulans would say, Sisko and Garak about whether or not to pay off the forger with biomimetic gel (or whatever it was), Sisko and Vreenak...come to think of it, it's very much a bottle show on the station, and has everything going against it there, yet it's very alive scene to scene.