Movie sound relies heavily on 2D sound design techniques as the viewer doesn't have control over what they are watching (scene by scene) and designers can only really work with left to right panning effects and volume fades to emulate real-world sound effects ie. passing cars. Game sound design techniques on the other hand are in 3D. In a game, the player controls everything they want to interact with and for this reason everything that can be interacted with by the player must have it's own unique sound effect. In this virtual world there are hundreds of set sounds which are constantly changing in intensity depending on how close the player is to the sound source.
If a player approaches a waterfall there will usually be a few sound sources to create in order for the player to believe that the waterfall is real. These sound sources would include the top of the waterfall where there is a constant flow of water and the bottom where the water impacts with a pool or river. To create these effects the designer couldn't just go straight to a waterfall and set up a mic and record the raw material because there would be too many negative artifacts to 'flood' the recording (birds singing, planes passing).
Instead, sound designers have to get creative and usually end up experimenting with tone generators and subtractive synthesizers which are capable of recreating pretty much any sound effect in the real world. For the top of the waterfall we would play around with various types of white or pink noise (TV static, audience clapping). But the best tools a designer can utilize are his ears and mouth. To find out what a waterfall sounds like I would have to try and imitate it by pressing my teeth against my lips and blowing air through the gaps in my teeth. The air being blown represents the water flow while the teeth act as the rocks in the river.
When watching a movie, if somebody pulls the blinds in a room, you suddenly hear the sounds of passing traffic but there was no outside sounds to be heard before the blinds were pulled. This is another 2D technique which only highlights the fact that the viewer is being guided on what to experience next in the movie. In reality, sound waves travel in 3D (expanding sphere) and this is something that the player's sense of hearing can identify with in a game which leads to further immersion into the virtual world.