I played this game a lot and for a very good reason. Majority of my game play consists of cooperative campaign with friends. There is still a whole lot of content from the community on the workshop that mixes in with custom maps, content, difficulty, and custom servers to mess around with. Even without custom content, the game is open for a huge majority of players no matter the skill, hence even players who aren't proficient can start on easy difficulty, and those who want a real challenge can play expert mode. Steam workshop has tons of customization to make the zombie experience much friendlier or more gruesome if you would like. Scripts that handle the game play differently like different animations or enabling certain features like crawling or extra dialogue to make the game more lively. Having over 2,500 hours with the included couple of hours on Xbox, its a masterpiece for me. #1 best game in my whole steam library from the time I've started gaming till the forever future.

Basically the first era of how I really love left 4 dead 2.