What's Up With the Ending?
Everyone gets a happy ending, that's what's up.
Sure, the President has lost his wife, but he saved the entire planet and showed what an awesome leader he is—so, that's got to count for something.
David and Steve also helped, having successfully traveled to space to disable the alien mother ship. The final moments of the film show David and Steve's joyous reunion with their respective lady friends, and suggest that those four lovebirds are going to live happily ever after.
Well, until the sequel messes that up…