Your friend has a very narrow view of success....though success is like Baskin Robbins. There's 31 varieties and everyone prefers their own flavor.

But it's hard to pinpoint a "profit number" when there's so many variables to consider (programming, production costs, post-prod. costs, testing, expectations, etc.). The "one size fits all" mentality doesn't sit still with profits as Muramasa turned money at 100K units sold while Halo 3 needed millions.

The only thing I care is when an obscure game (or RPG preferably) makes enough to warrant the release of another one. (Crosses fingers for Sin & Punishment 2's success.)