The free-to-play games.
Japanese company Taito had the inspired idea around 1978 that killing aliens was extremely good fun. So they invented a game called Space Invaders , lots of history then followed, some people got rich and so on... It's a simple game with simple graphics, but it has one of the most vital assets for any computer game — gameplay. Modern games seem to forget this with their fancy "3D graphics" and "millions of dollars." All you need is a pointy green thing which shoots white stuff at a rampaging