Although I've had a PS2 and then Xbox 360 for the last decade, I've never been completely into a game and emotionally invested in it as Forever Carefree said, since some old PC games such as Age of Empires the Rise of Rome, the Battle for Middle Earth, Europa 1400: The Guild, Total Club Manager 2003/04, Medal of Honor: Allied Assault, GTA III. The list could go on, I spend hours... days... playing PC games when I was younger.
Favourite game on the Xbox 360 is probably the first COD Modern Warfare, which blew me away. Having said that, although I haven't played it much, I think GTA V is probably the "best" game I've played, with regards to gameplay, although I don't like it as much as some old games I've played, if anyone gets me?