A simulation game with a dark twist, Plague Inc. has proven highly addictive even 5 years after it's initial release. Made by british games studio Ndemic Creations and published by Miniclip, this mobile game has over 85 million downloads and has won many awards.
The aim of the game is to indirectly control a plague which you can upgrade and evolve by spending DNA points. Win condition: eliminate all life on earth. There are many different types of plague you can choose from including common bacteria, parasites, and even special plagues like the zombie inspired Necroa virus and the mind controlling Neurax worm.
Overall this game has almost infinite replay value. Not only are there over 10 different disease types to choose from, there are countless pre-made scenarios and even custom scenarios. A simple premise with a huge amount of polish and care goes a long way and even in 2017 this game still holds up as a solid 7/10.