I just bought a new headset for my PC that I am quite happy with and which I think has great sound quality (once I fiddled with the EQ). I decided to test some games with it so I loaded up Left 4 Dead 2 and set it to 7.1 surround mode and proceeded to kill some zombies. Everything was clear and crisp and it was almost like playing the game for the first time again. I then loaded up F.E.A.R. 2 and was rather underwhelmed by the gunfire sounds. They lacked a certain amount of punch (I was especially let down by the shotgun). I then moved on to Battlefield 3 and was absolutely blown away by how great that game sounded. I knew DICE had a reputation for great sound quality but up until now I had only heard it through TV speakers or through a relatively inexpensive headset.
So, what games do you think have the best sound design and why? It can be anything from the soundtrack kicking in at the right moment to the staccato of gunfire or the sublime clash of metal on metal in a sword fight. From the little I've played since getting my new headset I'd have to go with Battlefield 3 as the best I have heard so far. All of the weapons from pistols to LMGs have a deep, meaty rumble to them that says "Hey, these can do some damage." Explosions are riveting and the sounds of helicopters flying in is either terrifying or elating depending on whose side they are on.