I have never heard of those games... I'm assuming they're FPS games?
X3: Terran Conflict / X3: Reunion:
The X-series is a series of space combat and economic simulation games made by Egosoft. They're known for their freedom and sandbox style gameplay an infamous for their unforgivingly steep learning curve. They typically feature trading of goods across several systems in a supply and demand based economy as well as combat involving many different kinds of ships and weapons.
Operation Flashpoint / Arma / Arma 2:
Military simulation, or at least the best you'll get for a home computer.
Think Battlefield series but more realistic.
They're all made by Bohemia Interactive, who also make the Virtual Battlespace series of training simulators, which is used by many armed forces around the world to train soldiers.
They're sometimes criticized by some for being realistic to the point of being unfun, but I don't think so since Arma 2 is my multiplayer game of choice at the moment.
-Falcon 4.0:
In my opinion probably the best combat flight sim ever made. It's probably the closest you'll get to actually flying an F-16. I probably spent a couple weeks looking over basic tactics to play this game effectively. The 400+ page manual is a real pain to read, but worth it in my opinion.
-Rainbow Six 3: Raven Shield:
In my opinion the last Rainbow Six game that was actually good. It's basically a tactical shooter like Operation Flashpoint and Arma, but focuses entirely on indoor combat, which has a completely different pace from the more outdoor, MOUT style action in Operation Flashpoint and Arma. Like those other tactical shooters, it's also sometimes criticized for being realistic to the point of not-fun, but I find it fantastic.
-Mechwarrior 3 and 4 and Freespace 2:
Mechwarrior is basically combat in mechs and Freespace is combat in space. They're not as steep as far as learning curve goes as the above games and not supposed to be realistic. Still, it doesn't mean they're easy to learn. Introduce them to a modern gamer who often has the attention span of a maggot and the first response tends to be "OH GOD WHAT DO ALL THESE BUTTONS DO?!!". :V
Basically they're all games that are not very simple and all of them use at least 75% of the keyboard.
By sharp contrast Touhou can be picked up in five minutes, and uses about 8 keys.