I really don't see this being the case. Any competently designed graphics engine has an abstraction layer between the app's graphics routines end the platform's graphics API. While it's not trivial, another API shouldn't be something that prevents an app from being ported to other platforms.

Did you completely miss just how much DirectX locked games into the Windows platform?

You mean the same that were equally available on Wii, PS 3 and XBox 360?

There's a bit more to it than that, though.

There wasn't much of a a perceived interest in gaming on the Mac and Linux platforms. The Mac and Linux graphics drivers were awful. A vicious cycle, which we're (hopefully) seeing start to break now. Mac is supported by at least some major games, which is a step forward. The Steam box should speed things along nicely for Linux, hopefully.

As pjmlp points out, games were successfully ported to different consoles, it's just that Mac and Linux weren't seen as worthwhile targets.

I suspect porting a Windows game to PS3 would be much harder than porting to Mac, but developers managed.