Mike West said:
"We're making a co-operative role-playing game - there aren't any co-operative role-playing games out there, we're the only one."
This isn't entirely accurate, I'm afraid. Back in the Nintendo Gamecube days, there was a turn-based RPG called 'Lord of the Rings: The 3rd Age' that had 2-player capabilities. Now, I'll at least praise Fable's co-op for being much better, since it's Real-Time and The 3rd Age had Turn-Based co-op (seriously, what's the point?).
But even besides that, you're clearly disregarding games like Gauntlet, Sword of Mana, X-Men Legends/Marvel: Ultimate Alliance, and Baldur's Gate. It begs the question "Just how many video games has Mr. West played?"
However, that's the only praise I will dole out for Fable's co-op. The game was easy enough without someone else helping you in combat and that was pretty much the only meaningful thing that your partner could do while playing. In the story mode, all the main characters would ignore your partner, even as (s)he ran around, waiting for the cutscene to end. Mr. West, it's not enough to simply be the only one offering a co-op RPG experience; it should also be meaningful and involving.
A good example of meaningful co-op is Dead Rising 2. While, yes, the 2nd player would not be addressed during cinematics, (s)he at least had the excuse of being omitted from the cutscene, so they couldn't mess around in the background out of boredom.
Anyway, the reason why Dead Rising 2 is a comparison is that it actually felt meaningful to have a partner. You and your 2nd player could multitask. For example, you could concentrate on distracting zombies while your partner led a few survivors towards an exit.
Sorry, Mr. West, but I'm afraid that Fable 3 was a severe step in the wrong direction overall. I say this as a gamer who actually liked Fable 2 and enjoyed playing it. I can't say the same about Fable 3.