What's the number a console needs to sell not to be a failure?

[Kantor]

I think the most important thing is that it turns a profit. The second most important is how it sells compared to its predecessor. The GameCube isn't considered a failure with 21 million sales next to the 33 million of the N64, but if the PS3 had sold 21 million to follow the 140 million that the PS2 managed, that would certainly be considered a failure.

Since all three console manufacturers had a very strong performance last gen, I think anything short of 50 million ought to be considered a disappointment.