At what sales point do you see a game a success?

[mowe]

For attach rate, 10% would be quite successful in my eyes. That would mean that 1 in every 10 console owners own that game (right?).

But this theory doesn't work for every game, especially those on the Wii. Hardcore games on the Wii have to sell to a lesser hardcore audience than the PS360. The many moms who own a Wii aren't gonna buy Metroid Prime.
So on Wii, any game over 600 000 is a success for me. While for the HD consoles, 1 million seems like a good benchmark for measuring success.