I agree. When you think about it, there have been no rockets from MS launched in Sony's direction recently (or vice versa for that matter), and nothing MS has done recently has impacted Sony; indeed, Greenberg has even praised Sony over the last few months.
But I think the biggest problem MS have to eliminate if they're ever going to be the market leader is that for the past two generations they've been copying and been fixated the market leader.
It's well known that they were fixated on Sony when Sony were dominating, and now Nintendo are dominating, they're completely fixed on Nintendo. They've gone from obtaining Sony's exclusives to almost turning their attention to motion control in the blink of an eye; and with Rare (and Lionhead as well by the looks) moving onto to full scale Natal development, it only emphasises this.
If they keep doing that, they're going to constantly be behind. They need to pick a target market and stick to it. If they are always focused on someone else, they're likely never going to be the leader.