Just plain fun
If I can think of one word to describe this game (excluding the words explosion, destruction, and awesome) it would be "fun". There are so few games that realize how important it is to be fun, and this is one of them. I have found myself just picking up the game from time to time to wreak havoc on the local EDF. The game allows you to do this in many different ways. I always felt kinda odd doing some of the missions though.... since many of them every very terrorist-esque in nature. Blowing up convoys, taking out bases through massive bombings... etc. Not that there is anything wrong with fighting the opressers on Mars, it is just interesting to see this side of the story. The game really captures the "Rebellion" feel very well. You feel opressed, and when you save some of your comrades, or thwart your enemies plots, you feel very involved. Freedom fighters was the last game I can recall that did this particularly well. Red Faction Guerilla is no exception.
