eg: ~100m iPhones (most recent data I could find was through Q4 2010 for aggregate):
Then compare to the top gaming platforms ever shipped:
PlayStation 154.59 million
Nintendo DS 147.86 million
Game Boy/Game Boy Color 118.69 million
Sony PlayStation 102.49 million
By that measuring stick iOS wins big vs. obscure consoles, but it also wins vs. the biggest and best.
ref - http://en.wikipedia.org/wiki/File:IPhone_sales_per_quarter.s...
ref - http://en.wikipedia.org/wiki/List_of_best-selling_game_conso...