Brad - That's what I've always liked about this game in all it's incarnations. You actually get to use your imagination while plotting galactic domination.
I'm sure there are some people who want scenarios, but I don't have much use for them. Don't play them in the Civ series either. It's me against the universe & woe betide the luckless race that stands in my way.
That's why I'll always have fond memories of Populous.