Having a happy ending is always a good thing. It's what folks expect. Problem is, so many stories are getting worked with tragic endings to the point where it's become expected, and then passe.
Twists to endings - that's the ticket! How about this: The city is burning, the heroes are fighting for their lives and the lives of their loved ones. Things are looking bleak and our friends are falling one by one. The enemy and it's reinforcements are about to succeed, tearing the planet a new orifice. The main hero fights desperately, thoughts of his beautiful family gong through his head, yet he still fights a losing battle. Suddenly without any warning whatsoever - Henry Winkler bursts onto the scene with a super weapon, reinforcements, and several crockpots of little smokies in Barbeque sauce. He fires his weapons, which, surprisingly sounds very much like a bean fart and fires little explosive marshmallow peeps. Instead of saving the hero, he lays waste to everybody and sets up a new government called "Winklerton."
See, left field isn't so bad. Although the orderlies are here to administer my medication. Squee!