In my own experience, from a creator's standpoint it's quite a bit different. You have to make sure pretty much every track loops well, and for non-cinematic music you don't really have the luxury of an "intro" section of a song; you have to hit the hook or otherwise the "meat" after the first measure at the latest. This is especially true of intro or menu music; the player is probably only going to listen to 10-30 seconds of the music before they move on to another screen that plays different music.
For someone who tends to make music based on "whatever sounds cool" and experimentation, it's very jarring to actually have to make the music accompany some on-screen, non-linear action and fit the theme of the game. It forces you to use instruments you might not be comfortable with (ex: an orchestra for a fantasy game) but also lets you explore instruments that would never fit in one of your personal tracks (ex: panflute and mandolin in an electro house track). It forces you to rethink your melodies and arrangements; it's surprising how bad or unfitting some non-game music can sound when played in a game, because it was designed to be the center of the audience's attention. Thankfully, because of this and the fact that the player is generally distracted with the game, the tracks only need to be about a minute or two minutes long, which is a lot simpler to make than a five-minute or longer track, and allows you to just focus on one set of patterns and be done with it. It's sort of like how a short story doesn't allow the space to develop subplots or excessive exposition, you've just got to get your point across and be done with it.
I've always looked at video games at a form of gesamtkunstwerk: an artistic medium where every element has to work to further the whole. It's unlike movies because you can't skimp out on certain elements. Each song is played a ton, the graphics will be severely tested, there needs to be a lot of writing if you're telling a story.
Film soundtracks are rarely played continuously. They're used in snippets. Very often, a movie soundtrack will consist of tracks that are 30-60 second hooks, since that's all the director needs. In any event, the soundtracks are tools to be used by the director.
In a video game, it doesn't work like that. Most tracks are played in their entirety and looped. It means that a song from a video game very often requires some integrity that a song in a movie doesn't need, because the song has to be replayable again and again without losing its meaning. Furthermore, game soundtracks are long. The Final Fantasy soundtracks started with 50 tracks in the original NES versions; the Playstation games ranged from 80 tracks to 160, which is incredibly long. That's longer than a good deal of operas, for instance (and back in Final Fantasy VI, an operetta was included in the soundtrack itself).
Gesamtkunstwerk is a term Wagner used for his operas, actually, and it's that operatic mindset that video games most remind me of. When you compose for a video game, you've got enormous potential at your hands: your music determines the mood of everything that happens. When you write, you're told how your tracks will be used, how they'll blend together, and that gives you an incredible freedom to really do whatever you can.
In my article, I mention how Nobuo Uematsu very frequently shifts genres: he's written waltzes and ragtimes and celtic pieces and rock pieces and piano ballads and he's had two pop hits, once of which (originally written for Final Fantasy VIII) sold half a million singles. If he'd been writing for a movie, that wouldn't have been possible: the best movie soundtracks all integrate around a sonic theme, similarly to how a symphony works. A video game's music is far grander: when you're writing over 4 hours of music for a single soundtrack, you can create music that goes over and over themes, and still have space for two hours' worth of whatever you see fit.
Because of the circumstances in which you're writing, you have a freedom to use your mind in a way that no other composer today really gets a chance for. It's similar to having a patron in some ways.
I've found that video game music can make fantastic background music while working - there's hardly ever any distracting vocals and it feels like you're attacking something mythic.
Movie soundtracks have a similar effect on me: The Incredibles, Dark Knight, Primer.
I've done the same. I think the best group of game soundtracks I've heard are by Jon Hallur Haraldsson, for Eve online. They really help to immerse you in the game universe. I think you can listen to some of the composers stuff on last.fm
Eve Online's music is hauntingly beautiful. Definitely one of the things that makes Eve so addicting: the music feels as vast as the game itself.
If anybody feels like importing the CD/torrenting it, Shadow of the Colossus's soundtrack (Roar of the Earth in English) is superb. I'd put it above most movie soundtracks. It's very subtle and very thrilling in all the right places.
In my opinion the interactive form basically allows a kind of meaning that is different from narratives. Environments, character designs, and other elements that are tangential to a narrative experience(such as music), often come to dominate a game more than anything in the story surrounding them.
Basically it comes down to the workings of the game mechanics; with repetition and reward/penalty systems they point the way towards deeper inspection of any desired element.
For someone who tends to make music based on "whatever sounds cool" and experimentation, it's very jarring to actually have to make the music accompany some on-screen, non-linear action and fit the theme of the game. It forces you to use instruments you might not be comfortable with (ex: an orchestra for a fantasy game) but also lets you explore instruments that would never fit in one of your personal tracks (ex: panflute and mandolin in an electro house track). It forces you to rethink your melodies and arrangements; it's surprising how bad or unfitting some non-game music can sound when played in a game, because it was designed to be the center of the audience's attention. Thankfully, because of this and the fact that the player is generally distracted with the game, the tracks only need to be about a minute or two minutes long, which is a lot simpler to make than a five-minute or longer track, and allows you to just focus on one set of patterns and be done with it. It's sort of like how a short story doesn't allow the space to develop subplots or excessive exposition, you've just got to get your point across and be done with it.