Iron fronts: liberation 1944 is a game on arma engine, if you can run it it is pretty good :).
omg u shud ply mw3 omg its so osm the graphics are super cool. <==== this is pretty much what all of my classmates would say if they could speak english.
Operation Flashpoint, anyone of them, i think the latest is Red River. Decent storyline, challenging gameplay, huge open areas, 4 classes, lots of weapons and pretty good graphics(and bullet drop).
You can give advanced orders to your team.
But OFRR is older