Mine has to be
Elder scrolls III:Morrowind
my dad had his Xbox for about 3 weeks at the time and I was plenty tired of playing the only game we had Which was Rainbow Six 3, so cool and I was good at it so his friend lent us like 3 games, now I don't remember what the other 2 were but once I played Morrowind, I was hooked to it, I obsessed over it, I lived and breathed to play it, my dad and his friend could easily see that I LOVED the game and he gave it to me for free, but I lost the copy he gave me at a friend house and he moved shortly after (Coincidence?) so my other friend gave me his copy that was under his couch (Which is so scrached it lags) so when I get so cash I plan to go out and buy the game of the year edition...I was 11 when I first played it and I'm 15 now and I still play it so many memories and good times, Oblivion was good, really good, but not OMG good like Morrowind was for me...