Aliens vs Humans – iPhone, iPad
A remake of the original X-Com game for the Apple mobile platforms, with very similar graphics and style.
OpenApoc – Windows, Linux
Port of X-Com Apocalypse, still very early in development. They can use all the help they can get!
UFO2000 – Windows, Linux
The only X-Com based game with multiplayer. Two players fight it out in a variety of maps and mission types with custom squads in traditional turn-based tactical fashion. Works over Online, LAN and Hotseat.
UFO: Alien Invasion – Windows, Mac, Linux
An open-source X-Com remake made on the Quake engine.
UFO: Extraterrestrials – Windows
A commercial X-Com based game, very similar to the original, very fun, and with a huge modding community supporting it. There’s also a sequel in the making but it’s gone quiet for a long time.
X@COM – Windows
X-Com in a roguelike version (not to be confused with a roguelike version of X-Com). Perfect if you’re just sick of those pesky graphics getting in your way and miss ye olde days of ASCII glory.
XCOM: Enemy Unknown – Windows, Xbox 360, PS3
The XCOM IP is back! Official remake made by Firaxis, adds a whole bunch of new stuff but also brings back all the beloved lore from the original.
Xenonauts – Windows, Mac, Linux
Currently the most promising new X-Com remake around, brings back all the classic original gameplay with new graphics and features. Currently in alpha phase but you can try it out by pre-ordering.
Xenowar – Android, Windows
Another mobile X-Com-like game, features very simple cutesy graphics.
Missing in Action
The EDF Project
One of the earliest and oldest X-Com remakes, EDF boasted a lot of cool features and had high hopes, but quickly crushed them when absolutely nothing came of it.
Project Xenocide – Windows
SupSuper worked on this! Sadly it didn’t last.
UFO: The Two Sides – Windows
A promising multiplayer remake of the original X-Com that was sadly cancelled for reasons still not quite clear.
UFO: Cydonia’s Fall
An X-Com remake made in Unity. Permanently put on ice apparently. Cool globe prototype though.
UFO 2012 – Java-based phones
A mobile game based on X-Com with very similar tactical gameplay but much more simplified management and strategy. The website just disappeared one day.
An X-Com based game made in the Unreal engine. Not much has been heard from it but it looks interesting.