OldFatGuy: Accuracy can be addressed. Anything that requires WASD movement should have controller support. Anything that requires your hands on the keyboard at all times should have controller support. Mouse clicking games only don't need it, where clicking the mouse controls a majority of the action.
That's just the problem, the only way it can be addressed is via autoaim and or screwing with tolerance. There just isn't the capacity for precision with a nub that you can get with a mouse. Especially somebody that's gotten used to using a mouse can very quickly hit a tiny portion of the screen.
The way that they make controllers work these days is by removing the accuracy requirement via auto-aim or increased tolerance both of which are just workarounds for the fact that controllers lack the necessary delicacy to handle those sorts of games.
OldFatGuy: I'm not saying do away witih keyboard support, I'm saying every game that uses the keyboard mostly should ALSO include controller support. It's just a fact that that is easier to learn and master. Believe me, console makers tested all sorts of things to see which was the easiest and most capable. And they've all ended up with a variation of the same thing, a controller with movement mostly controlled with the left hand and action controlled with the right hand, all on ONE device, a controller. I'm sure that's probably another slap against the minority for being left-handed, but it is what it is.
It's a trade off with some genres of game. With any FPS it effectively can't be done as you'd have to rebalance the game for controllers and keyboard+mouse. Other genres are more forgiving and could handle both without too much trouble.
I'd love to see those Halo players go up against the Quake and Unreal players mixing it up between console and computers, but I have a hard time believing that it will ever be possible. Consoles generally cheat to make it work. I lost the link, but there's a great blurb from one of the developers of Halo about how much cheating they had to do to make online play work.
Also, consoles have always had controllers going back to the days of pong, they're not going to add a keyboard and mouse because that would be more expensive and people who want that tend to buy PC games anyways. They ended up with the standard gamepad because it was flexible and was generally the least bad option they had available.