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

[The Ghost of RubangB]

For me it's a case by case scenario.

Depends on the developer, the franchise (new IP vs. sequel vs. licensed game), the development cost, the userbase of the console(s) it's selling for, and the developers expectations (when available).

For example, when a game like GTA4 costs a billion times more than GTA3 to develop, and is most likely not going to sell as much, the standard success metric gets a lot shadier.

However, some smaller games like Carnival Games and Cooking Mama are huge successes. Cooking Mama basically saved Majesco from the brink of death.