Faster than light is a simple sci-fi that seems to do everything right. Its a single player roguelike real time game that puts you in charge of your own space ship.
This recently released indie title was put together by a two man team and even includes an awesome accompanying musical score that helps set the mood. It may be Sci-Fi themed but the system requirements for FTL are far from futuristic...
Faster Than Light PC Minimum System Requirements
OS: Windows XP / Vista / 7
RAM: 1GB Memory
GPU: 1280x720 minimum resolution, OpenGL 2.0 Support, and recommended dedicated graphics card with 128 MB of RAM
HDD: 175 MB Hard Drive space