Mac vs Windows vs Linux is an old debate but maybe for the first time it's got interesting.
Apple sell the Mac as a package, beautiful hardware with an attractive and simple interface that is easy to use. It knows who it's marketing to and as a share of home users this is growing as people realise that they can do everything they need to for home use without having to have Windows. If this continues, games developers won't miss out on the opportunity to sell to this market.
Unfortunately Windows is the defacto standard for business desktop use and doesn't look likely to change anytime soon. This means that most of the time who needs to take their work home with them are tied in.
Linux remains the enigma. Not developed by a sole entity and therefore without a cohesive marketing strategy it develops in many directions in a more organic fashion. While some distro's remain focused on highly technical users others are out there trying to get their product out to the average home user. These organisations are making admirable efforts in doing this, and I include Ubuntu and Linux Mint among them, however these efforts are relatively recent and as far as catching up with Apple's efforts have a long way to go. Admittedly so does Windows but as the most used system can easily rely on general familiarity without having to make massive strides in this area.
If home users, who like the steadily growing Apple user base, realise that they don't have to have Windows thought that a Linux distribution was a viable alternative and was available for free then Linux on the desktop might find momentum. It's great credit to Ubuntu that they have made great efforts in this area. Vista is the 1st of the Windows line I've ever heard non-technical users criticise and this is what will make the next five years of this debate interesting and why Microsoft are hurrying to develop another release.
Those Linux power users who criticise Ubuntu should remember that they are making constructive efforts in both the business desktop and home desktop arenas and whether they want to use it or not, it is currently them that are driving adoption Linux forward more than any other party. I'm sure they would have to agree that the world would be a better place if less un-technical users were using Windows on their desktop.
This is not a simple choice between three systems but a complicated battleground being fought on many fronts. Competion is healthy and I for one hope that both Mac OS and Linux distributions enjoy an increase in market share and keep Microsoft on it's toes.