What are some alternatives?
When comparing Insurgency and Urban Terror, you can also consider the following products
Destiny - Destiny is a loan management solution that allows you to configure and customize to manage your own lending business.
Xonotic - Xonotic is a free (GPL), fast-paced first-person shooter that works on Windows, OS X and Linux.
Arma - Experience true combat gameplay in a massive military sandbox.
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.
Quake - Quake is a series of first-person shooter video games released by id Software.