Well, if VGChartz is to be believed then:
PS3: 37 months 30.10m units sold 813,513.51351351351351351351351351 per month
360: 49 months 35.80m units sold 730,612.2448979591836734693877551 per month
Wii: 37 months 62.59m units sold 1,691,621.6216216216216216216216216 per month
That's pretty amazing. That's 82901.2686155543298400441257584 more PS3's sold per month than 360's. And, that's more Wii's sold per month than PS3's and 360's combined, but who's surprised?
I'm sorry about the decimals, I just figured that they may actually make a difference, especially if somebody wanted to do their own math.