I just finished Phoenix Wright: Ace Attourney. I bet I took the longest of any one to complete that game. It probably took me about three years of random playing and a very detailed walkthu.
And in light of the release of Pokemon Black & White, can I just say I have only ever finished one Pokemon game. Silver. And I don't actually know where it went. In fact, I'm still playing Pokemon Yellow. This is how epic I am.