If you were computing back when 3D games were just taking off, you'll remember that the cream of the crop for sound was always some iteration of the SoundBlaster. Everyone supported it and a huge number of prebuilt machines came with it. What's the market look like today, though? With huge numbers of boards shipping with acceptable, if not quality, onboard sound, with many other vendors offering hardware accelerated sound and a host of other reasons, it seems today that Creative may be just a tiny fraction of the audio card market, maybe as little as 1%:

If average sales price of an audio card is $100, then Creative Labs ships about 324 thousand of audio cards per quarter, meaning that less than 1% of 57.15 million PCs sold per quarter include a discrete audio card by Creative Labs.
They are faring considerably better with the Zen, but still don't hold a candle to the behemoth that is the iPod. The day of SoundBlaster dominance is long since over, but I had no idea that they'd been relegated almost to a bit player. It makes sense, though, when I think about the last three machines I've built. All of them included onboard sound that supported 5.1 or better, with audio quality enough to satisfy. While a SoundBlaster may sound better, apparently it isn't enough to convince the PC building masses. Overall, audio cards are only 10% of Creative's business.