What are 3-5 really unique video games?

Meaning that they really stand out on their own and no other game is similar to them at all.

Portal/Portal 2 is a pretty unique concept - I don't know of another series quite like it.

Basically allot of valve games

Katamari Damacy

I would say the Super Mario Galaxy series. Old game, yet very good graphics, and very one of a kind, for it is set in space and it has a very mystic ending.