I can say, I've played quite a lots of them:
- X-COM: UD
- X-COM: TFTD
- X-COM: Apocalypse
- UFO: Extraterrestrials (couldn't really get past certain poing despite several tries)
- Jagged Alliance 2, 2.5, Wildfire
- Silent Storm
- Silent Storm: Sentinels
- XCOM EU 2012
Games I've tried but couldn't really get into them:
- The UFO series with active pause - real-time and SLS don't mix very well.
- Fallout Tactics: BoS - as a harcore Fallout fan I was gravely disappointed this not being Fallout 3 and boycotted the game. Tried to play it lately - not that bad, but doesn't have "that something".
- UFO: Alien Invasion - played some early build, half of things weren't working.
- Some turn based Warhammer 40k game - meh
- Hammer&Sickle - RPG based on Silent Storm placed in Cold War theme. So much potential, so poor execution