There were a lot of games that hit a million downloads. Super Monkey Ball must have hit it a LONG time ago. Everybody bought SMB when the app store "opened."
Maybe, maybe not. Sega did announce that SMB sold 300,000 copies in 20 days when it was selling for $9.99 = $3,000,000! (Source) and it did remain in the top 100 for a long long time. Also, Crash Kart Racing, which Apple listed as the all time best selling app not too long ago, was probably the 1st to 1M copies (see this page). MacRumors posted an article about sales figure when Apple had 1Billion downloads promotion (link) with the no. 2 app, Koi Pond selling over 900,000 copies. And Pangea announced that Enigmo sold upwards of 700,000 copies, netting a cool $2M along the way.
