I agree with Frogboy. xP 1. Have a personal story to tell. 2. Variety of aliens. 3. Explore the planets and the galaxy. 4. Electronic/ambient/synth music 5. Hence the story, write some characters that fulfill the story project.
My favorite games can probably change in the future. Most of my favorite has been science fiction ones and they're personal to me. Star Control 2 is still my favorite science fiction game that has inspired me a lot of SF aspects. 1. Mass Effect 1 2. Mass Effect 2 3. Another World 4. Mass Effect 3 5. The Way I can name the rest of the games that weren't in my list, but these are the ones I