Immortal on 24 August 2012
Objectively? Probably Mario Kart Wii, with well over a 1000 hours (and another 500 hours of having left the Wii on without actually playing). Not quite my favorite game, but everyone loves it so I ended up playing it very frequently.
I've got like dozen or so RPGs at well over 500 hours, though, and I'd probably say Dragon Quest IX or Pokemon Emerald are the games that really gave me the most value for their price (especially since they were individually roughly half the price of Mario Kart).
“These are my principles; if you don’t like them, I have others.” – Groucho Marx
