I thought District 9 was better than Aliens, so from where I'm standing things aren't quite as bad as they might appear. Sunshine was also pretty great at showing the loneliness of spaceship life. Additionally, if you were to include Children of Men in the genre (I wouldn't), it would make things look a lot more positive for the genre today.
Anyway, even in the late 70s to early 80s, which I think was the best period for film sci-fi, the truly good science fiction films were pearls in a sea of crap.
As for K-Pax, it was a shallow, phoned in Hollywood machine attempt at making a quirky, sappy, yet smart movie about life and belief.