What are some alternatives?
When comparing Quake and Unreal Tournament, 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.
Doom - Doom is a science fiction horror-themed first-person shooter video game in which players assume the...
AssaultCube - AssaultCube is a FREE multiplayer first-person shooter game. Taking place in realistic environments, with fast, arcade gameplay, it's addictive and fun!
Overwatch - Stylized team-based FPS
Counter-Strike - Counter-Strike is a PC-exclusive FPS video game developed by Valve Corporation.
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.