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've played them.