Apple still has a significantly higher market share than Mercedes, and nobody has said that Mercedes is going out of business soon.
What's more, market share statistics can be skewed several ways:
1. Sales only in the U.S.
2. Sales worldwide
3. Sales to repeat buyers
4. Sales only through retail outlets
5. Sales only through mail order outlets
6. Sales over a certain period of time
7. Existing usage base which happens to be as high as 10% according to Fortune magazine. The reason the sales is not as high a percentage is that Macs last longer. It is a double edged sword, build a better machine, and less people will buy from you frequently enough to make your marketshare numbers appear as high as you want them to be for developers to believe in the platform.
At least with emulation, all but the most complex 3-d PC games will play on the Mac. With PCs you don't have emulation to take you past Mac OS 8.1 on a PC.