Joust is a game which really needs no introduction. I'm sure that you will have heard of it before. If not, Joust is a game where you play a guy with a pole riding around on an ostrich and using said pole to knock other jousters off their birds.
The graphics are nothing special - it only uses orange, red and a dark green for everything - but they work well together, and don't hurt your eyes as much as a standard CGA game, although they do tend to get a little boring after two hours. But if you really can't deal with it, just go play the VGA version.
The sound, of course, is very basic, consisting of only a few beeps and buzzes from the PC speaker, but it is done quite well, and doesn't annoy at all. Some of the sound effects are actually quite well-placed, such as your ostrich sliding to a stop.
Overall, while it's not amazing, it is a good game (especially if you are bored) and worthy of a 4. And, dare I say it, I doubt that arena-based games like Unreal Tournament would exist without this sort of precursor.
The only thing that needs to be kept in mind here is that the game will run too fast with anything over about 3000 cycles.