This has been out for awhile, and I actually owned it when it first came out however I was lacking something my first go around, and that was having a co-op partner to enough non-stop mayhem with.
For being an older open world game the graphics are really not that bad, add on top of that everything can be pretty much leveled and its actually a marvel that the game runs as good as it does. There are some texture issues as well as some graphics disappearing all together.
The sound effects are pretty solid ranging from the gunfire, to the sound of an artillery strike dropping onto your target. The only compliant I have with the sound is a weird glitch I encountered while playing co-op, when me and my buddy were raiding an enemy location I would get a weird echo effect when the AI would try and alert their boss, it also kept playing even when killing the caller it was kind of annoying but really doesn't detract from the overall game.
Very few games come close to the fun I have had while playing Mercs 2. I know most of it is mindless running around and blowing stuff up, but what makes Mercs 2 unique (well for its time) was being able to approach a mission in a variety of different ways and still be able to have fun doing it. What is also fun is coming up with new attacks using a co-op friend my personal favorite being the jihad jeep (c4+jeep+speeding to the enemy building or tank) which by the way created alot of laughs, and pulling off a dramatic escape while one person flies a chopper and the other calls in a bunker buster on the oil platform racing to grapple the chopper as the structure crumbles into the ocean. Some of the missions can get repetitive and some get down right frustrating (I am looking at you cargo missions) but if you look past that and have a buddy to play with you will have a ton more fun with it.
I give Mercenaries 2: World in Flames a solid 3/5. Overall it is a blast to play despite the glitches and come on its like dirt cheap right now so go ahead add it to your game library.