Die Meat Boy Die!!
Its really a fun game that gets you hooked big time. the precise controls and the level layouts are awesome. the best part is that many secrets retro style gaming is involved.
2D never got better than this. the fun of being exact yet dying each time trying to get to your Bandage girl is an awesome thing that keeps you wanting for more.
The replay at the end of a tough stage shows all your tries in one go and makes up for all the frustration and hard controlling.
Also, with so many extra characters to play as each level gets easier or tougher when playing with other characters. This just gets you to play more of the game.
Overall an excellent simple game which gets all age groups to play retro 2D big time! :)