Dragon Age: Origins - I spent about a hundred hours on my first run-through.
Mass Effect - One of the few games which my immediate response to finishing it was to play it again. And I can't help but be a completionist.
Warcraft franchise - Between WoW and War3 I've spent a long time on this series.
Pokémon franchise - Spending 250 hours on a run-through of these things was standard practice for younger me.
"HOW CAN YU TRET MEH LIKE DAT"