I just know from experience that the more work I put into making the game fun for my players, the more fun I wind up having.
A character died last session after two years (in real life) of adventuring. Personally I find permanent death fun... I like the shock, the sense of gravitas, knowing there are real consequences... But I left it up to the player, and they really want to keep playing their character. So we are finding a cool way to bring them back.
Even though their fun is a little different than mine, I know that my experience as a DM is going to be better because I'm making the game more fun for my players.