There were 30 third party million-sellers (shippers) worldwide by the end of 2008.
See text next to fifth slide: http://www.nintendo.co.jp/ir/en/library/events/090130/02.html
75 million is likely the total sales of all third party software on Wii in the US according to NPD. There were ~170 total games shipped to "The Americas" by the end of 2008, so that would sync.
Last page:
http://www.nintendo.co.jp/ir/pdf/2009/090129e.pdf
By the way, along with the 30 third party million-sellers, I believe there were at least 18 first-party million-sellers which were known from Nintendo first-party million-sellers lists over the yeras, and possibly 1 or 2 more if some games sold 1m total, but not in a single year. So there were 48-50 total million-sellers for Wii by the end of 2008 by Nintendo's shipment numbers.
"[Our former customers] are unable to find software which they WANT to play."
"The way to solve this problem lies in how to communicate what kind of games [they CAN play]."
Satoru Iwata, Nintendo President. Only slightly paraphrased.
