I've played games on the computer for longer than there has been anything resembling today's personal computers, and I occasionally enjoy going back to the simple "roots" games of yore. One of the classics of text simulation, an ancestor to Sid Meier's Civilization, is Hamurabi (intentionally misspelled due to an eight character limitation imposed by the shrimpy computers and programming languages of the 1970s).
I used to play Hamurabi over a Unix connection to a Bell Labs mainframe. The game, by today's standards, is ridiculously simple. You govern the city state of Babylon. You buy, sell, and allocate land for farming, and tell your people how many acres should be farmed. Your people thrive or starve based on your decisions. Random events such as plagues and rats hamper your ability to grow your city, as does population pressure. The game is a constant balancing act based on simple text and mathematical formulae, yet even today it's diverting.
It's also just a few lines of code, condensed now into a Java applet. Give it a spin for a hundred turns or so, and see what the state of the art in gaming used to be.