Its no simple matter; its a full time job for at least 6-15 months, with a team of between 2-80. For example, when I worked at SCEE we ported Little big planet

Its no simple matter; its a full time job for at least 6-15 months, with a team of between 2-80. For example, when I worked at SCEE we ported Little big planet to PSP from PS3, and that was 14 months with 40 odd people full time. It can be much quicker than that, but in general you have to worry about getting the engine working on the new platform.