Woah, hard question.
Think i'm going to have to go with videogames though.
No matter who it is, you WILL get sick of the other person in 365 Days, especially since there is no privacy at all. And you will get sick of that person FAST. Not that it matters, because even if you go till half-way getting along fine, there would be still six months of open or hidden contempt left.
There is no way this could end well.
Of course, you will get sick of Videogames too, but while they are less effective, they will be at least a longer distraction. Also, with EVERY Game and Plattform, you won't even get JUST games. Think about stuff like Mario Paint, Little Big Planet or something like that. With games in wich you can create something, especially something wich is not a game, you can waste even more time.
Build a Computer Engine in LBP, or create a chiptune magnum opus, and even if the PC doesn't come with one, there's got to be a game with a rudimentary word-processor, wich creates even more distraction through creative expression.
That said, i'd guess both options will eventually end in insanity and possibly suicide.
But with Videogames, at least i don't have to care or get by with anyone else, so not only another person will have to suffer, i can also spend my days without having to mind another perosn. And, as said, with games you will probably be able to do more than just game.
