Microsoft must be pretty happy. Awesome 3rd party game sales on the console. Big opener for Bioshock 2, while Mass Effect and MW2 continue to perform, Not only are they handily outselling the PS3, they pretty much have a full deck of cards to play.
They should take advantage of the momentum and drop price now right in time for Splinter Cell and Alan Wake, ride out the summer then Halo Reach launches, then Natal. If they really play their cards right they could be the #1 selling console in the States this year.
PS3 was supply constrained. Expect them to come back big next month with FFXIII and God of War. Should be neck and neck with 360 or even edge them out.
I don't know how the Wii was supply constrained. I saw them everywhere in February. Anecdotal, I know, but I'm just not sure if I buy that at least here in the United States. PS3 on the other hand I know was sold out at a few places in my area last month.