Minecraft - 10/10. Occupied me for 2009-2011 which is an eternity in video game years. Best indie game ever made.
League of Legends - 8/10. Occupied me since I stopped minecraft to now (2011-2013). -1 point because community can sometimes suck and -1 point because the game isn't completely bug-free.
Katawa Shoujo - 9/10. Only occupied me for a week, however has changed my entire view on life. Even stimulated me the stoic into near-tears. -1 point for some storyline flaws.