What do you define as 'good sales'?

Exclusive - 1.5 Million

Multiplat - 2 Million

It all has to do with the expectations of the game buy the gamers and the devs themselves. How much money it cost to make, whether it was advertise a lot or not and lots of other stuff. Mathematically it would look like this.

By those calculations, Demon's Souls did well in sales.

Any game that is easily capable of matching and surpassing the money put into it. This could mean 10,000 units sold for a game that cost $50,000 to make and costs $10 to buy.

it makes a profit and warrants a sequel

88mphSlayer

good sales past 1 mil

great sales past 3 mil

When developer/publisher revenues exceed development costs.

Enough to make a profit.

If a game sells enough to satisfy the developer/ publisher. And if there are plans, open the door for a sequel.

Its good if it makes a profit, but on average 1 million is good. Usually for new IP's and exclusives, really popular games and sequels should probably get above 3 million or so if they have a lot of hype and a big fanbase.

If it gets a sequel, pretty much.

It has to sell as much as Halo 3 or Gears of War or else it's a horrible failure.