If M$ want to crack the japanese market they need to flood the market with the usual japanese crap.
Seriously, there are literally thousands of games released in Japan every year, and the law of averages tells us that once in a while a game will be good... they're the japanese games we get over here.
But the japanese top 10 games probably arn't a huge proportion of the market. I mean over here the top ten chart probably counts for a large majority of the sales. In japan however, go into a video game store and for every person picking up a copy of a top ten game there are five picking up crap like "Dog racing bets", "Waterskiing bets", "Wuzel fights monkey man for money"... seriously... gambling games are HUGE. And the others are weird... From what I can gather strange crappy rpgs, pointless "hit 3 buttons in time to music to pull of a speacial move" scripted fighting game, and weird ass gambling games make up a lot of the market.
I'm not saying all japanese studios are crap... some produce excellent games. But Japanese people like weird games... yes they'll want an xbox 360 for DOA4. But if they can't get their strange games fix to go along with it there isn't much else to draw them towards an xbox 360.