Depends on if it's running off of an 8-bit game's engine or not. I'm writing an OST for a game that's all chiptunes, but I'm not into tracking (learned at one point, forgotten it all by now) and his game doesn't require me to. I wrote a fakebit album using nothing but magic 8bit and 3x Osc with custom waveforms sampled directly from the NES, as well as some DPCM drum samples for all the chiptune stuff (though only the first track is 100% NES authentic as far as limitations). The first track emulates the VRC6 chip to spec, and the second very closely does (Ben added a string sample from A Link to the Past, and in some spots it uses 2 noise channels, albeit rarely). It really just depends on how the game is running
If you want those DPCM samples, I'd be happy to send them to you
EDIT: Nathan beat me to it, that dangus. Still, the offer for samples stands (and for anyone who wants them)
Also Nathan's description of NES hardware is just the basic 2A03 sound chip, but there are a lot more than that as far as expansions go (check out Xenon Odyssey's album Fountainhead for some good examples of lots of them). Just do a bit of research and figure out what limitations you want to impose on yourself. I personally like VRC6 because I have a bit more breathing room for delay and chorusing (both of which use a full channel because they would need to be hand sequenced if it was in a tracker)