I think if Zack and Wiki sold 500,000 it would be considered a success. The problem imo is that it was a new IP with no hype for it. Yes IGN raved about it but many of the mainstream Wii owners were not familiar with it. They should of come up with a better name as well. Something simple like Treasure Hunter: The Quest for Gold would of been better. It sends a simple message to casual gamers. Sadly I see Carnival Games will do much better sales wise than Zack.

Anything under 1,000,000 for a nintendo is a bust.

For the rest of the simpletons? under 500,000 is a bust

Many low budget games (like Zack and Wiki) have such small development costs that they can break even after less than 100,000 units are sold to retailers; if a publisher made $20 off of each copy of a game that was sold (which is a reasonable estimate for a $40 game) a $5 Million game, which would be middle of the road for a Wii game, would require sales of 250,000 to break even.

I think it is fair to call any game that is unprofitable a flop ...

A game like Zack and Wiki is going to be very difficult to categorize in either category though because it will likely end up bringing in a ROI similar to some of the better selling games of the year, but at the same time will (probably) not sell more than 500,000 units.