I really like RPGs so I would vote for that but I think a fighting game would be pretty easy to make. Here's my pitch:
The GB fighting game:
Jeff and Ryan argue about something stupid which polarises the office. Maybe some sort of bet which Jeff loses but refuses to drink the gin(or a better story). Other staff members begin to take sides and this splits the office into Good guys and Bad guys. This should be presented as an animated cut-scene before the actual game.
Each character is based off of a staff member or honorary staff member. Their fighting guy personas are themed off of the staff member's video game tastes. Then there are unlockables for some of the honorary staff members.
Jeff: Shooter guy?
Patrick: Horror games guy
Brad: Death only makes him stronger. Maybe berzerker or necromancer type.
Alex: Bad games
Drew: Red baron themed or Top gun themed.
Ryan: Point and click guy.
Vinny: RPG guy. His special is 'bag of holding' and he throws all his loot on you that he has been hoarding.
Alexis: no idea
Matthew rorie: Special attack: Puppies!
Dave: PC gamer. Hits with a keyboard and whips a mouse.
Cool baby: Cool baby ain't on nobody's team.
John Drake: The man with infinite energy
That's one idea. It could also just be a random tournament for 'Best in Press' and there are no teams. They just compete bloodsport style for the title.
Also we forgot one game that could be made...Lincoln Force!