Who doesn't love a good happy ending (no, not that kind)?
Sure, the movie, TV show, video game or whatever needs to earn it, but when done right, and if the series calls for it, then there's no viewing experience more uplifting than when it all comes good at the end.
The hero saves the day, the ultimate villain gets defeated, the will they/won't they couple finally get it together, and life has seemingly worked at pretty well, allowing them all to ride off into the sunset with the TV show able to rest in peace and going out on the terms both creators and fans wanted.
Of course, some TV shows couldn't possibly end on a high note. It wouldn't be true to form for The Sopranos to suddenly finish on a positive, or for Twin Peaks to bring us closure. But others, say a Spaced or a Parks & Recreation, needed to leave audiences satisfied in the way only a happy ending could.
But then there are the TV shows where the endings seem at best joyous, and at worst fine enough, but are really hiding some dark truths underneath the surface (it goes without saying, but spoilers from this point on).