You bastards!
(Spoilers ahead, obviously.)
I actually thought they'd done it too.
Last episodes are always tricky things to get right. There are certain fundamental elements the audience wants, expects, demands. And top of that list is a happy ending. We've lived with these characters, followed their adventures... laughed, cried, got angry and shared every other emotion with them... for eight whole years. If we're never going to see them again, we want to know they're riding off into the sunset, that they've finally found happiness.
The problem with a character, and a show, like House is that its basic philosophy goes against all that. In real life, House always reminds us, for some people at least, there are no happy endings. They've made a big point of that over the last eight seasons. Just when you thought you knew where a story was going, they always managed to pull the rug out from under you. That's the nature of good detective fiction (a genre which House has always belonged to - don't let anyone kid you it's a medical drama): there has to be a twist at the end that you didn't see coming. So much of the storytelling in this show is built upon dramatic irony... so when House's best / only friend Wilson was revealed as an oncologist dying of the very disease he's been helping people deal with throughout his entire medical career, it would have been a huge cop out to have House cure him. Even though House cures everything!
So Wilson had to die. And House had to either find another reason to go on living... or follow / precede his friend to the grave. Because the only other option would be to give in to sentimentality, and this is a show that has fought sentimentality at every available opportunity.
That's why I thought they'd actually killed him. Even though I knew they couldn't. Despite the fact that it was the last ever episode, despite the fact they'd titled it "Everyone Dies", despite the fact that it would have been the ultimate dramatic irony: the final lesson House learns for definite - there are no happy endings. Just like he'd been telling everyone all along.
In the end though, it would have been a colossal bummer to end the show like that. So they found a way to have their cake and eat it. House dies, he loses / sacrifices the only thing that gave his life meaning. And yet he lives. Why? Because the world's biggest misanthrope cares more about his best friend than he does himself. So House and Wilson get to ride off into the sunset after all... not a happy ending if you dwell on it, but for that one perfect moment, exactly what they - and we - needed.
Goodbye then, Gregory House M.D. I'll miss you, you cantankerous old bastard.