OpenTTD

Let's start with an oldie but goldie. To get the basic idea about the game, let's quote the OpenTTD website: 

OpenTTD is an open source simulation game based upon the popular Microprose game "Transport Tycoon Deluxe", written by Chris Sawyer. It attempts to mimic the original game as closely as possible while extending it with new features.

You are put in charge of a new transport company with a hefty loan from the bank but no infrastructure or veichles. Since you aim to be a tycoon, your goal is to make a fortune by connecting cities and industries and charging for the transport. 

A nice, fan-made clip.

OpenTTD is a real-time strategy game that is easy to pick up but hard to master, which is always the quality of great games. The gameplay (adopted from the original) is smooth, relaxing, fun and addictive. What makes OpenTTD great is the abundance of user-created content, which is easily downloadable from within the game menu. There are endless possibilites of costumising the game with new veichles, buildings, economic models, scenarios, aritifical intelligence and even more. This means that you can always spice the game up with something new, and adds greatly to its lasting appeal.

I really cannot recommend this game enough. The game is open and free but if you like it, please donate at their site, because the developers are really doing a great job with this one!

Installation:

• via Sofware center,
• by executing in the terminal: sudo apt-get install openttd

Links:

•  Official OpenTTD website