Transport Tycoon Deluxe was originally released for DOS in 1995 and for Windows in 1996. In the game you play the role of a, well, transport tycoon. You build and manage networks which use various types of vehicles to transport goods and people across maps that vary in size, environment and land layout. OpenTTD takes the original game and updates it to run perfectly on modern systems among other improvements.
Originally only playable if you owned the retail product, now anybody can play OpenTTD through use of free user-made graphics and sound packs. The currently available graphics pack closely matches the original graphics and as a result isn’t the most eye-catching thing in the world. However, there is higher quality graphics pack in the works so you’ve got something to look forward to in the future.
If you like Tycoon games and can deal with some dated graphics until a better tileset is available then I’d highly recommend giving it a go. There’s a lot of content in this small package for fans of the genre.
If you own the original game you don’t need the free graphics or sound packs, naturally.