Development-wise that problem has mostly been solved. In the past cross-platform game development was done as separate projects, often handing off "porting" the game to a platform to an external team, even. Today it's more common to use engines (such as the unreal engine) which support all the major platforms (PC, 360, and PS3 typically, for first-person, high graphic-load style games), and then do the development for all versions concurrently. Typically you'd just have your regular builds set up to produce versions for each platform as a matter of routine, and you'd have a consistent testing experience for each. You'd still end up with customizations and tweaks for each individual platform but for the most part all of the hard work of targeting and optimizing for each platform is automated.