DOOM (id Software)
It’s fair to say DOOM changed everything. DOOM had it all. Lightning fast 3D, evocatively detailed texture maps, and varied and dynamic lighting in each level. It also featured floors that weren’t all at the same height - there were steps and everything! And the .WAD file system let users add their own custom content to the game in one of the first instances of truly accessible modding. Best of all, DOOM embraced the only gamer power fantasy that could beat shooting Nazis: being a space marine shooting space demons.