What are some alternatives?
When comparing Quake and Doom, you can also consider the following products
Xonotic - Xonotic is a free (GPL), fast-paced first-person shooter that works on Windows, OS X and Linux.
Unreal Tournament - Unreal is a series of first-person shooter video games developed by Epic Games.
Call of Duty - Call of Duty is a first-person and third-person shooter series by Infinity Ward.
Overwatch - Stylized team-based FPS
DotA 2 - Dota 2 is a Free-to-play, Action-Adventure, Multiplayer Online Battle Arena, Single and Multiplayer video game created and published by Valve Corporation.
Team Fortress 2 - Team Fortress 2 (TF2) is the sequel to the game that put class-based, multiplayer team warfare on...