If only Linux suppliers would get together and decide on one fraking API for 3D, sound, and input devices it might happen, Of course, a standard installer would be nice as well. A standard UI as well.
I could on and on. Linux is its own worst enemy, as UNIX has always been. Technically, the Linux/UNIX OS's are far better than anything Microsoft has shipped, but it has never tried to be anything other than a niche product best used for server use. The occasional turnkey graphics workstation is really the only application success UNIX has ever had and that has waned.