VGChartz: “By 2006 the PlayStation 2 was slowly being phased out and a new console generation was beginning to take over the market. Over the previous several years the Metal Gear Solid series had become synonymous with Sony's home consoles and carved its place as one of PlayStation's heavy hitters, alongside the likes of Final Fantasy, God of War, and Ratchet & Clank, among many others.
As a result fans were eagerly awaiting the next big chapter in the Metal Gear saga on home consoles. However, before the series would make its jump to the next console generation it took a slight detour in the form of a series of titles for Sony's PlayStation Portable, starting in 2004 with Metal Gear Acid and an eventual sequel. Those two games are essentially non-canon spin-offs. In this article I'm going to focus on the two main PSP titles that are seen as part of the series canon storyline - Portable Ops and Peace Walker.”