America's Army is a very well programmed game. The weapons are done beautifully, with fully animated controls and reloading, bullet drop, recoil, stoppages, manually extending bipods, etc. The comms system is really cool. You can whisper to teammates, shout out loud, talk on the radio, or give hand signals. I would play it more if there were single player / co-op missions. Also the maps are very small. If they change those two things I probably would play it A LOT.
OFP is awesome. Big maps, combined arms, very realistic interactive world. But I find that multiplayer is very laggy, and the multiplayer interface is awkward and missing a lot of features. The interaction between players and buildings is really bad, so it's not too good for fighting in towns and buildings. I found single player to be very addictive though.
Raven Shield is really good. It's a modernized Rainbow Six. Kind of a cross between America's Army and Rainbow Six. The maps are kinda small though. And the weapons models have all the limitations or other Red Storm games. No bullet drop, can't shoot through walls, can't climb obstacles, etc. Graphics and sound and enemy AI are fabulous though.