Play a game backwards and describe it.

[Fish]

 Braid, You find out how the events that happened really took place.
Anyone who's played & beaten it will understand.  =P

[Kilroy]

Mario Party backwards is about giving stars back to toad while slowly going around in circles losing (and occasionally gaining) coins until you get back to the start and lose 10 coins for ending the game.

[JrDude]

In Yahtzee you put dice into a cup.

That's forward in Yahtzee too ;) (You can't throw the dice out unless you put them back in)

[Kaso]

In DDR, you spew arrows from your feet.

[Silverhawk79]

In Guitar Hero, you shoot circles into the distance.

[Kilroy]

In Guitar Hero, you shoot circles into the distance.

In Rock Band, you shoot speed bumps into the distance, along with long green and orange lines at the top.

[Linkman]

In Animal Crossing you earn money while your house shrinks.

[Lotos]

In the Donkey Kong arcade, you give a princess to a giant monkey and descend down a flight of steel bar thingies.

[Totla]

In Luigi's Mansion, you shoot ghosts out of a vacuum into your house, then lose it.

[Syzothermy]

In TF2, you pull the cart, give intel to the other team, and the goal is to lose all of your cap points.

[Dog Food]

In Clue, you try to forget whodunit.

[Kilroy]

In Super Mario Sunshine, you pollute a city while slowly making it darker and darker, then you fly off the island and everything gets better.

[noodle976]

In bomberman, walls try to trap you into a corner and creatures rise from ashes to shoot beams of fire to create bombs which you collect as you retreat from the closing walls.

[SkyMyl]

In The Game, you win every time you don't think about it.

[Ares300]

In Elder Scrolls 4: Oblivion, you set loose a daedra prince, scatter lost relics the emperors son needs, open portals to the realm of oblivion, and kill the emperor.