For some strange reason...

[Dog Food]

Or, I could go on a quest for the three Hallows.

Animal Crossing [Game Cube] - It would take forever for someone to get every single unlockable. Also, the old one is so outdated that few would want to play this version to the end, when they could be playing Wild World or City Folk.

Harvest Moon [Whichever is longest] - Honestly, it would take a lot of sheer willpower to get through every single day in this game, as well as unlock everything in the process. I can barely make it to Year 2 in Harvest Moon: A Wonderful Life before getting bored.

And any other never-ending games. Oblivion and Fate (or a game of a similar title, can't remember the exact name anymore) are examples (at least I think. I've never actually played them, only watched, and from what I gathered they don't actually end).

Or, like I stated above, I could just kill Harry Potter and rob him of his Invisibility Cloak, knick the Elder Wand (seeing as I've killed Harry Potter, I'm the true owner), and find the Resurrection Stone hidden in the forest. Then again, if I did both, I'd cheat death doubly! That'd make me immortal x2 compared to the rest of you lot.

[Sgt.Chilly]

Or, like I stated above, I could just kill Harry Potter and rob him of his Invisibility Cloak, knick the Elder Wand (seeing as I've killed Harry Potter, I'm the true owner), and find the Resurrection Stone hidden in the forest. Then again, if I did both, I'd cheat death doubly! That'd make me immortal x2 compared to the rest of you lot.

Well Oblivion Has  a Main Quest Storyline that Ends but even after there is still Several Side Quest Stories, and then 100+ Dungeons (Caves, Ruins, Fortresses, etc) to explore, dozens of unmarked quests, Favors of the Deadric Princes, Finding the Masters of Skill, Enough One of Kind Equipment to outfit a small army ( I actually have a house to house all of my weaponry).  So yea I've logged like 200+ hours and still haven't got everything.

[Lohn Jocke]

Shadowrun, because it's online-only.