According to a presentation by Cammie Dunaway of Nintendo. 

First 18 months software units (US):

Wii - 50 million (not including Wii Sports)
X360  - 28 million
PS3 - 20 million
PS2 - 42 million

First 18 months hardware units (US):

Wii - 9.5 million
X360 -  5.2 million
PS3 - 4.2 million
PS2 - 8.5 million

http://kotaku.com/5010214/nintendo-wii-has-highest-software-sales-for-first-18-months

damn i didn't know its software sales we so good. i wonder what percentage is third party software.

Wii beated the PS2... nice...

Wii better than PS2? Very nice

Did some calculating using US figures for the time periods given on that chart and it appears that 29 million units of software are from 3rd parties.

The interesting fact is that is still more than PS3 or X360 overall totals.

Not including WiiSports or VC titles.

Even if you take out WiiPlay, it's a record.

And the Wii very recently beat the 360 in worldwide software sales to date.

Stop with the lies. The internet said that no one plays with the Wii anymore.

Hmmm...

50 million x ~$50 (Guitar Hero is more, some games are $40)

~$2.5 Billion in Wii Software in 18 months.

~139 million Wii software revenue per month

If Nintendo had 75% market share for software on Wii 3rd parties would have ~$35 million per month.

But realistically, Nintendo doesn't have that much market share in the USA so theres probably ~$60 million/month on average for 3rd parties to fight over through 18 months, and that number is growing.