Can you provide an example?
How about Microsoft Flight Simulator X, using all features of an Nvidia GTX 670 card which are supported by the game?
I haven't run into anything that Linux "can't play".
Can you provide an example?
Amazon streaming video can't be viewed on Linux, as far as I can tell. Hulu+, which I believe uses Silverlight or somesuch Microsoft nastiness is also not Linux-compatible. I was going to set up a media center around MythTV, but ran into that stumbling block. Since then, my PS/3 has gained the ability to play from these sources. Also, the next TV I buy will be able to play these things from its own Internet connection, so it's becoming less important for Linux to catch up.
I'd also like to run StarCraft II, am I'm not sure that can run on Linux, although I haven't looked into it.
The question is not what it can play, but what it cannot legally play in the US without buying proprietary codecs, due to license issues.