Alan Wake if you haven't played Alan Wake you need to play Alan Wake, if you don't know what Alan Wake is its Alan Wake.

Scribblenauts series
Kirby Canvas Curse
Spec Ops The Line
Terraria
NSMB Wii
Metroid Other M
The Conduit
Red Steel 2
Boom Blox series

Yeah!  Maybe I'm mistaken, but I thought it was a physical release before it got put onto the Xbox marketplace...but at any rate, yeah, there's definitely a disc version.  I saw a used copy in a local Gamestop earlier this year, but if you can't find it in a store you can find it on Amazon, I checked there just now.

definitely demon souls, the best hidden gem this gen

Excite Truck and Trauma Center: New Blood on the Wii were the only niche games I bought and enjoyed this gen. I'm a mainstream gamer.... :/

I going to put another vote in for Alan Wake.

Thanks!  Founnd it on Amazon for only $20 and ordered it :).

I came in here to say, "Just bought 3D Dot Game Heros and played an hour. Feel like this game is going to be a gem"

El Shaddai instantly comes to mind for me (despite the game breaking and me not being able to play any further)

Demon's Souls at first, but it gained popularity damn fast. Xenoblade, Ni No Kuni (haven't played, but I hear good things)