And now get the hardware peripherals to work. The gaming mouse with a polling speed that XWindow cannot handle. The programmable flight sticks that can't be programmed in Linux because there is no tool (and no, sorry, the windows-tool doesn't work in Wine). The EAX-7.1 Sound card that is treated like it can only output Stereo (and that gets no driver from its manufacturer). The USB Soundcard that doesn't work at all (for the same reason). The gamepad
Yes, all those examples can be brushed aside with "That's not Linux' fault that their maker doesn't deliver drivers" (well, except maybe that mouse issue, that's really a shortcoming of XWindow). True. But guess what, the user doesn't care whose blunder it is. What he sees is that these things he paid multiple 100 bucks for do work in Windows and don't work in Linux.
And until we solve this, it's going to be a really hard sale that "Linux on the Desktop" idea.