Well yes, sound is a big element in games. It helps create environments in a virtual area and without it it would be less entertaining and unrealistic. Like watching a silent movie without the person playing a piano piece - its quite pointless to say the least. Used for interfaces, weapons, sounds of footsteps and things, action cues for the general sounds and also music. There are many composers and its hard to say what the key composers are, I know a few since this is the genre of music which I like and listen to quite often. Quite a large amount are Japanese especially with the NES systems but there are others from different countries that have worked with it but mainly the ones that are more modern are where these other people specialize.
I cant really say what my key moments of sound/music in games are, iv mainly been interested in Star Wars games but they take music pretty much from the originals that John Williams have originally created but in the Knights of the old republic (particularly 2) i liked the soundtrack used and it was more original in comparison to others. The Halo soundtrack also was another impact on me again with its theme and its use of sound. And also Call Of Duty had a really good use of sound for the effects as well as the gunshots, and developments in soundtrack.
At first I didn't know what the *good times* song was until i seen it on youtube where I recognized it instantly. Compared to other performances this one seems to have more people involved in it. 3 Main people on front backed up with quite a lot of other people and backing singers. Combines traditional rock band sections with some Jazz instruments. Makes it quite successful just initially looking at it. In terms of influence im not sure because it just seems to be another song created. Looking into it I didn't actually realize that Nile Rodgers worked with the soundtrack for Halo 2 and 3. "Sumthing currently focuses on distributing a fast-growing new genre: video game soundtracks. Soundtrack titles include Halo, Halo 2 and Halo 3."
Since this person worked on this video game soundtracks genre its quite influential since its one of my favorite genres.