Ctrl+Alt+Del already has some pretty good 10 commandments. Though if I remember right, it may be more than 10...
Beyond that, I object to the fact that the current prototype of the commandments doesn't have a single command in appreciation for gaming as a single-player artistic experience. That should be half, at least. Or maybe artistic and competitive gaming each have different commandments. Possibly also another set for "just for fun" gaming, since many people just playing for the lulz tend to ruin the experience of those playing as serious competition, or to appreciate the game as a work of art.
Beyond that, I vote for the gaming gods to be based on genre. For instance,
The Prince of Persia: god of Action games
Mario: god of Platformers
Master Chief and Gordon Freeman (feuding brothers): gods of First-Person Shooters
GLaDOS or Tetris piece: god of Puzzle Games
Cloud Strife: god of RPGs
And so forth.
As for a holy book... I'm not sure there is any one book for it. Maybe... the internet. Just the internet. Though it would be an incredibly flawed holy book...
EDIT: Though it must be noted that gaming couldn't really be a genuine religion simply because it has no promises regarding eternity. And if it did, that would be stupid.

It would make a great prank similar to the Australian Jedi Census Incident though...