It seems wrong to just go over the Nintendo hardware shipment totals, so let's look at the other guys. Unfortunately there's not as much interesting to show for a number of reasons: Sony and Microsoft no longer give out separate shipment numbers per region. Neither PS3 nor X360 are setting records in a high or low way. Since Sony switched to their modern method of shipping they've only given the quarterly/yearly numbers rather than lifetime totals, which means for the moment we've lost track of where PS2 and PSP are at.
I'm trying something different for this post. My images can be made at arbitrary sizes, but at a size for column width here things don't look their greatest. Last time I made them bigger but gave the image tags a smaller size, which looked halfway decent in Firefox 3. However, in browsers that use simpler methods of image resizing (IE7, Firefox 2) those images look pretty awful. So as a compromise, I'll display the images created with a width of 400, but if you click on them they'll be created at a larger size. So the images shown here are not just smaller thumbnails of what the larger version will look like.
X360: 20.3 million. PS3: 14.37 million. Wii: 29.62 million. X360 and PS3 have on the whole performed similarly since PS3's launch, but PS3 does seem to be catching up: this is the third straight quarter PS3 has outshipped X360. In the last three quarters, PS3 has outshipped X360 by 1.88 million.
For the first year of each system from launch, they shipped very similar numbers. However, PS3 has continued to ship decently large numbers, while at this point in its life X360 shipments were pretty slow since they'd overshipped in the previous holiday season.
As I said earlier, they're not breaking records in a good or bad way. How do they compare to other recent secondary/tertiary consoles, though?
Pretty decently, actually. Both are above last generation's GCN/Xbox, and appear to be around N64 shipment territory. N64 and Sega Genesis are historically the top secondary systems, doing in the low 30 millions. That two systems at once are doing this well is pretty impressive. If they don't drop off as quickly as N64 did in its later days, they could become the new secondary/tertiary champs. Since both systems still have a lot of room for price drops and no party seems in a rush to launch the next generation, this seems quite possible.
However, they'd both have to do a hell of a lot better than N64 to come to the sort of totals currently predicted by users of the simExchange: 62 million (X360) and 73.5 million (PS3).