Slimebeast on 14 February 2010
Even though Oblivion is by far my most favorite game it can get boring once in a while after you've played well over 1500 hours.
So I'd say Age of Empires II. Always when I get back to it I get amazed by how fun it is. And the reason why I quit is not that I get bored, it's that I get consumed by it so much that I eventually force myself to take a break.
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