When I say underrated I don’t mean Conker’s bad fur day, Wonderful 101, or any other game with a cult following! I want you guys to give me the games hardly anyone knows about the games you can’t even find the full soundtrack to online! Mine would be Ikachan for the 3DS, great game and someone needs to put the main theme on YouTube and not s remix of it!
My answer would probably be EDGE. It's a puzzle game developed by Mobigame, initially released for iOS and Android but later released for PlayStation Portable (that version is also playable on PS Vita and PS3), Nintendo 3DS, Wii U, Windows, Mac and Linux.
You roll a cube around a stage, collecting Prisms to increase your speed, and you're trying to complete one of many stages as quickly as possible. It's a simple concept that's used incredibly well, with many well-designed levels, although it does get really hard at some points. My favorite level is one where you land in a robot made of cubes that takes you to another part of the stage.
It's a crying shame that the most exposure this game ever got was due to a copyright dispute. It's a great game with a surprisingly great soundtrack to boot.
not really underrated, but the original paper mario for the nintendo 64 is pretty much buried under the thousand year door, and no one really talks about it anymore though its a great game