Well, if there was internet, I would probably do the cheating thing and choose guitar hero or rock band with the infinitely many DLCs. However, a game that is ever-changing or being updated would work as well. Maybe WoW...
However, the best choices land in the sound room. I mean, cmon... Dream Theater probably secretly released a 5.9-month long song somewhere around the time the earth cooled, after Jordan Rudess and John Petrucci traveled back in time using Rudess's Korg Oasys. Either that, or I would loop an idoser track for 5.9 months straight. A dose that would put me in a long, lucid dream, in which anything I ever wanted would be right there for me, only to wake up shortly before the 6 months are up, and spend the final day meditating on the events in the past. Yup, I win using the least liked room...