NSMB wii is doing outstanding in sales.
So far it has only dropped below 1 million sales world wide once. It has only been out for six weeks and already has 8.2 million sales. I did a little digging and compared it to Halo 3 since it seems to be the game to which many modern game sales are compared to. I am not comparing it to MW2 since it is multi-plat.
So here we go. It took halo 3 52 weeks of sales to acheive the 8.2 million sales. it only took 6 weeks for NSMB Wii. I don't know about you, but I find that to be really amazing.
Here are the comparison chart links:
NSMB Wii (the wii chart is not updated to dec 26th sales week yet): http://www.vgchartz.com/swlaunch.php?game1=New%20Super%20Mario%20Bros.%20Wii%20-%20Wii[35076]
Halo3: http://www.vgchartz.com/swlaunch.php?game1=Halo%203%20-%20X360[6964]