Correction, Microsoft is having to subsidize JRPGs. KRPGs, WRPGs and the like are doing well on Microsoft systems.
Orange Box should have a similar drop to most other major FPS games - a 60% drop should be expected.
Beautiful Katriami is going to be a very odd game to predict. I wouldn't expect huge sales week-1, but could have Viva Pinata type legs. For refference, VP debuted at #65 in January, with 1,099 units sold. It now has a 20x multiplier.
Other genres can sell well on the X360 - fighting, WRPGs, racing, RTS games are all big sellers on the X360, and sell better than their next-gen counteparts, and have alot of breakout games. In the case of Western RPGs, there's been a huge surge to the X360 for those type of games (when you have a game like Two Worlds look to sell 400k in the US alone, and maybe be a million seller, you have a good software mover).
But I do agree the X360 needs a stronger family and JRPG base. Those are the 2 weak-er bases. VP has sold reasonably well (300k), as well as a slew of other young teen titles like POTC3 (which vastly outsold the other versions).
This kind of basis should come this Christmas, since Eternal Sonata and Blue Dragon will be on-market for awhile, as well as news of Lost Odyssey. If MS can get JRPGs to start selling well in the west, the X360 will retain the lead as the go-to platform for every genre out there for a long, long time.
Because lets face it, it's still the top-tier platform for litterally every genre right now, outside of ultra-casual titles. Even then, you have the XBLA selling really, really well on games like Uno.
As for Ace Combat 6 - I have very, very mixed feelings. On one had, I feel it'll easily do 100k, and hit 150k and move alot of hardware. However, I've never seen it on the Famitsu most-wanted charts: is it just a title that no one might care about, or a title that no one needs to list, but will buy anyways?
On the US/PAL side, however, I think AC6 will probably out-sell the Japanese LTD numbers in 1 or 2 weeks in the US. AC6 has the huge advantage of being within 2-3 weeks of the November boosts in the US and PAL, and those numbers might lead to AC6 averaging over 50k every week from debut till the end of January. If it secured those type numbers (which it should), it will easily cruse to 1m w/w (which I am anticipating 1.4m or so).
Merely because the X360 has the advantage of getting alot of older PC-core gamers that have jumped to X360 since it has half of the top-tier PC library. AC6 could be seen as a succuessor to the Falcon and Flight Sim series (despite being vastly more arcadey), and wind up having great legs as a must-have definitive flight game. And the multiplayer will help too.