the 1 mil mark is a mile stone but i really have to go with 2mil plus before i will give the game a nod, but install base has a big factor in what i think it should get,

if the game sells above the avg game on that platform then it is a success

Anything titles by Nintendo that doesn't sell 10 millions is a flop.

Wii = 5 million+
X360 = 2 million+
PS3 = 1.5 million+

1 million...

It varies, first party should have a large attach rate, while 3rd parties are usually held on a lower standard and if its a niche title I say if you can hit over 250k then you're doing fine.

I will always try and look for profit. What else is there? If GTA had sold only 1.5 million copies, would it have still been a succes?

As someone said, profit+fans equal succes, nothing else.

To everyone saying sales numbers:

If Game A sells 1 million copies, but loses $5 million while Game B sells 500k copies, but makes $5 million, how is Game A more successful than Game B?

I think a game is a success as long as it covers its costs and turns a profit.

By that definition, each console has ~5 successful games.

I guess it would really depend on the budget of the game, and to some extent the genre (JRPGs generally sell less than shooters, for example).

Well i think this cannot be generalized under one number for example one million. Games like No More Heroes don't cost as much as titles from other platforms, there were no big advertising campaigns , and developers were happy with sales. So does this game can be considered a failure?

I think all variables should be taken into account: hype, genre, budget, installed base, console etc. etc.

Production cost has to be included in determining if a game is a success or not.

Look at movies.
An independent film that costs $1m to make and grosses $25m is a huge success.
A summer blockbuster that costs $200m to make and grosses
@ NightstrikerX
Using your "20% attach rate = success" equation, there were no successful PS1 or PS2 games.