The core difference between a corridor shooter and a sandbox shooter is that in the sandbox shooter you can play it your way. You could opt to make hit and run raids with a vehicle, or make a distraction with remote controlled mine and take your objective with little trouble while the guards are investigating. I hope that Far Cry 2,which allows you to do all these things, becomes the prototype for the genre.
Far Cry 2 takes place in Africa, and you play as one of 9 mercenaries from foreign countries. Your brought in to take out the arms dealer know as The Jackal, but that soon goes wrong when your character contracts Malaria. You eventually find some pills, and after a brief tutorial you are flung into a war torn Africa. The UFLL(United Front for Liberation and Labor) and the APR (Alliance for Popular Resistance) are tearing the Savannah apart with constant fighting.
The towns are all under ceasefire, but you will find plenty of guard posts hanging around the Savannah.
Far Cry 2's open ended gameplay flow like this: Get a mission, which are available at almost every point of interest. Find a vehicle, and walking is not an option. Most missions can easily take place 10 miles away from where you received it. Then you have to scout the opposition, marking points of interest on you map. Then you have to formulate a plan. The worst approach is to go in guns blazing. Then,after getting past the guards, you finish up the mission and find a new one.
The gunplay in FC2 is different than most titles.Hip firing is totally and completely inaccurate, so you have to look down your iron sights. This system works well, and it cuts off all those stupid run and gun things we are used to using.Most enemies can take about 5-10 bullets, though one snot to the head kills instantly. Some of the new mechanics are great though. First is fire. Fire is no longer just a lame effect confined to one small area. It spreads quickly through the dry grass,and tactical use of it really helps with an assault. It can go inside buildings and is even affected by the wind. When used properly, fire will force you enemies out of their cover or alienate them from the fighting.
The other cool thing is that enemies no longer just walk around. They have to eat, sleep, patrol at certain times, clean their weapons, check for ieds and socialize.
Far Cry 2 is incredibly innovative and just comepletely amazing. expect a full review soon.