If you're a company (like Capcom) and you can spend somewhere between $100,000 and $5,000,000 to port a game (potentially with some new content or upgrades) to a platform and sell 500,000 copies wouldn't you do it? You'd be looking at a profit of $5,000,000 to $15,000,000 which could be used to offset current development costs.
Certain games (like Okami) often sell far worse mainly because they're released on the wrong platform, at the wrong time, or against tough competition. A publisher can take a game like this and produce an upgraded port to another system in the hopes of recovering lost money and potentially building a franchise.







