The mouse and keyboard are far superior as controls [to what is available for a console]
I wouldn't be so sure. Though a lot of PS3 and PS4 games support a USB mouse and keyboard, an analog joystick offers finer control of movement speed and direction than WASD, which are equivalent to the 8-way directional pad that's been around since the NES. And what do players 2 through 4 use, especially in games where sharing doesn't mean splitting?
and the processor speed and graphics are superior to any console.
But at what cost? Say you want to build a gaming PC so that it can be used in the living room while someone else in the household is using the PC at the computer desk. Can you build a PS4-equivalent second PC for $400?
But one thing I'll grant to PC gaming is mods.