You can play in a window with Command-M (from memory). This is less than ideal though as the mouse will move outside the bounds of the screen all the time.
Stretching is less than ideal because the images become quite warped.
I have definitely installed and played SC/BW under Snow Leopard and I can't recall having issues with the size of the image (if that is what you mean). If you are asking if you can get smoother graphics on a modern larger monitor, or a widescreen mode, the answer is no.