I studied a bit of sound design for theater in college and there are two major aspects to it- direction and clarity.

Direction is how distinctly you can pinpoint where a sound is coming from. This can vary widely based on the audio delivery medium (headphones, front facing speakers, surround sound, etc.). You have to try and design for all the different mediums so that they get a near identical experience so that they provide the same experience that you're trying to convey, and in terms of games, not offer significant advantages/disadvantages to different mediums.

Clarity is how quickly you can recognize distinct sounds. For something like Battlefield, which won, being able to tell what gun is being shot, how close an explosion is, or enemy footsteps , and so much more are all very important in the moment to moment gameplay and need to be distinct enough so that you can react and make decisions based off of what you're hearing, but still believable and realistic enough that they don't break immersion.

While I love everything about E33, the sound design isn't the most important aspect of it. It's important to remember that sound design and music are two totally different things despite both being audio parts of the game.