We will only be focusing on running the server parts of games that do not require desktop interaction. Instead, you run the client on another computer and connect to Pi. Some clients can run on Pi's X desktop, but they might suffer from low frame rates.
OpenTTD is a reimplementation of the original Transport Tycoon made by Micropose. The game is dangerously addictive and adding Internet play into the mix gives you an extra competitive edge.
You have to have a passion for logistics, strategy, and real-time simulation to enjoy this game. The goal is just something to do with controlling trains and trucks as efficiently as possible and make profit while transporting cargo.