What game should I play next?

Castle Crashers :)

If I already haven't played them I'd go for Bastion and Hammerwatch. Both are awesome.

Bastion is an action role-playing video game developed by independent developer Supergiant Games and published by Warner Bros. Interactive Entertainment. In the game, the player controls "the Kid" as he moves through floating, fantasy-themed environments and fights enemies of various types. It features a dynamic voiceover from a narrator and is presented as a two-dimensional game with an isometric camera and a hand-painted, colorful art style. Bastion's story follows the Kid as he collects special shards of rock to power a structure, the Bastion, in the wake of an apocalyptic Calamity.
Hammerwatch is a fantasy-themed hack and slash action-adventure game. It was released on 12 August 2013 on Steam. The game was developed by Jochum Skoglund and Niklas Myrberg. It was mainly inspired by the Gauntlet games.

Thank you all for your suggestions, but does anyone else have more suggestions? Maybe with reasons as to why I should play it.

Trine 2 is an amazing game. Took me I think 8-9 hours to beat the main story getting most of the collectables. There's more levels after the main story too. It's a great puzzle platformer, probably the best I've ever played.

Far Cry Primal man, it's a epic game (for me), i love prehistoric games like this one!

Far Cry Primal, Trine 2, The Long Dark, This War of Mine, many good choices. :P

Wasteland 2: Director's cut (most recent version), because it's an awesome game set in a similar setting to Fallout. Might take more than one week to finish though. Mass Effect 2, it's an awesome space FPS game with a cool story and dialogue options like Fallout. Stanley's Parable, because it has absurd humor which I love. It's a rather small game so should be finished rather quickly within less than a week probably.

dead space 2 :3

Torchlight II - because in one week you can win the game and you will feel satisfied and done with it. But for that week you will be immersed fully.
Great game.

The Stanley Parable. If you haven't played it through a couple times, you definitely should. One of the best humor related games in my opinion.

Undertale. I think it starts out a bit weak and at first and I wasn't feeling the jokes either. Actually, I thought it was good but not amazing. That is until I made it to the end. It has a really satisfying ending that ties everything up. And after watching a few let's plays I started to notice all the little detail the game has, which is I really love in games, and I started to like the jokes more too. I was a bit cold to the game at first, but now I really think it's one of the best games I've played in a long time. Just make sure you play it in pacifist mode, or you will have to play the game again to experience all of it. As good as I think the game is, I wouldn't have liked to replay it right away.

I saw two good ones with little/no playtime right away.

ARK:Survival Evolved and Borderlands 2 :O

Torchlight II, Mass Effect 2 or Dead Space 2.

Thanks for the input everyone, I think I have what I need.