killzone 2 most likely.

Multiplayer - Just Dance
Single Player - Super Mario Galaxy

Super Stardust HD

I was amazed at how much time I spent playing this very simple arcade game. The reason it was so fun? Short bursts and could be challenging, while not frustrating.

Fallout 3.

Tekken Revolution

If I had to pick one it would be Oblivion but Halo 3 and Smash Bros Brawl come tied second

In single player:
The Souls series, Donkey Kong Conunrty Returns, Metroid Prime Trilogy, Dead Space, Portal 2, Resident Evil 4 Wii
For short breaks:
New Super Mario Bros DS, Mario Kart DS
In multiplayer:
Mario Kart Wii, Tekken 5 Dark Resurrection Online.

I just can't pick one.
Probably a tie between Demon Souls and Dark Souls 1 on top.

KOF XIII.

Fallout 3

Probably Pokemon Pearl on the DS (My first pokemon game!)