1. Ratchet & Clank: A Crack in Time
Like seriously. This game deserves so much more love than it gets. It's friggin amazing.
2. Skyrim
Regardless of what people say about it, this is the sort of game that will still be played in decades, because of it's "reputation" among PC gamers. And also it's great, so there's that.
3. Portal 2
Back when Valve still made games, they made gems like this. It was also the third (huehue) franchise to get the Valve treatment, aka getting two loved main entries, but never getting a third, because Valve doesn't like money.
EDIT:
4. Super Meat Boy
Because.... it's awesome....