Like Dwarf Fortress, Mount and Blade is a computer game which involves complexity that is tedious to deal with in a pen & paper game. Specifically, it deals with the command of a hundred or more troops, equipped with a variety of horses, arms and armor. The gameplay is almost pure action as you control one individual who gets into the thick of battle while issuing commands. There are numeric attributes, skills and proficiencies which have some influence, but the player's action skills are more important. The most distinguishing feature of the game is its mounted combat - it is the closest to real and visceral jousting, horse archery, ride-by sword slashes, etc. that you can get from a computer game.
I bring up this game on my blog mainly because of the feel that it evokes. Nothing will ever compare to our imagination, not even big-budget movies, but the game does a good job of making you feel the tactical realities of the day. You can lead heavy horse charges through seemingly-invincible shield walls and see the enemy be sent into total disarray. You can expertly shoot a light lancer who is pursuing you, and see his limp body take five seconds to fall off his horse. You can plunge your pike into the heart of an oncoming knight's steed and see him tossed face-first into muddy dirt. You can ride circles around slow heavy infantry and pick them off one-by-one with your bow. You can send such a great quantity of missiles against your foes such that their shields shatter and fall, and their blood covers the ground, as they scatter and flee before they even make it to melee range.
In particular, I enjoy battles between two groups of heavy knights. It almost feels like an air battle, depending on the terrain - I have to work together with my underlings to cut off the paths of my enemies and deliver decisive blows. If I choose to use a bow, I must be able to thwart my enemies' attempts to shake me off as I shoot them in the back. If I bear a lance, then I must figure out the exact timing for when I make a sharp turn and try to skewer the horses of my foes. If I end up dismounted, then I have to find some trees and slash everyone who passes by, eventually grabbing and jumping onto the next unoccupied horse.
Best of all, the game is extremely open-ended and has no story to restrict you. Instead, you make the choices of who you hire, when and where you lay siege, which kings you curry favor with, whether you aid or raid a village, and the greatness of the battles you take part in. The only real limit is how many troops on a battlefield your computer can handle at a time.
I have not even gotten to the fan-created content, of which there is a great abundance. You can get a better idea of what a massive Jedi-versus-Sith lightsaber battle might be like through the Star Wars mod, see a panoply of war banners arrayed under your command, defeat cavalry charges with massed musket fire, set up your seneschals at every village in the world, found holy knightly orders, and much more.