Dr. Mario on the NES is one of those classic puzzle games that looks simple but gets seriously addictive. You're dropping colored pills into a bottle, matching them up with viruses to clear them out—sounds easy, right? Then the speed picks up, and suddenly you're frantically rotating pills mid-air trying not to mess up your whole setup.

The music is weirdly catchy too—that little jingle when you clear a line sticks in your head for hours. And if you've got a friend around, the versus mode turns into a ruthless battle of who can screw up the other's strategy first. It's aged way better than it had any right to.