I picked up RollerCoaster Tycoon 2 on GOG after learning about OpenRCT2. Pretty much it's an open source engine that allows the game to run on modern operating systems really easily. I've never played any RollerCoaster Tycoon before, but so far I've been having a great time with it!
You can't copyright game mechanics. So, if you replace the sprites with legally distinct ones and write the code yourself, there are no laws broken.