(er I never said you said anything about MS flight sim, that was part of *my* point )
The mantra of PC gaming is *either* compromise *or* multiple paths. Developers have shown they nearly always go for multiple paths rather than compromise, especially if it has any effect on playability. Play a game like Beyond Good and Evil - there is a multiple path between the mouse+keyboard control scheme and the gamepad control scheme. Both actually work, though the gamepad is much better. The gamepad experience isn't compromised to make the mouse and keyboard one work though.
It could be the same with GoW - adding a mouse and keyboard scheme is not going to compromise the game to the point that reviews shout about how awful it is and no-one ever buys the game. Even if it was awful they'd just say 'you really need a gamepad to enjoy this game - and hey it works best of all on an X360 pad plugged into your PC'.
Yes you can - the lack of a decent experience with keyboard and mouse does not stop many games from being made - including driving and flight games. If GoW requires a gamepad then so be it - it'd still sell well.you simply can't build any reliance on these peripherals into your games if you want them to sell