Resident Evil 4, epic epic game. My favorite horror survival game besides Silent Hill and American Mcgee's Alice. Wasted countless hours playing this game, I would often play this game nonstop on the weekends, forget to take my medication, then experience some paranoid episode late at night while playing it. Graphics were great, storyline was interesting, and the ending was solid. The mini games provided additional gameplay once the game was beaten. Though only a one player game, the challenge and thrill of the game provided much replay value.
The Megaman franchise gets a lot of praise, and although I remember Mega Man 2 being a solid game, I can't vote against one of my favorites here.