Yeah, and people custom designed screens for each resolution. It was a different world. You could never take a 640x480 VGA game and play it in 320x200.
Yes, you could -- and people often did if they got better performance out of 320x200. When SVGA cards became widely available, multiple resolution support became a hallmark of even some of the DOS games of the day. Especially 3D ones, but I remember being able to play Jazz Jackrabbit 2 (a 2D platformer, and a Windows DirectX game) at 320x200 or 640x480.
