As far as "serious" games are concerned, Half-Life 2 and Far Cry 2 are my favorites. The latter especially does a good job of portraying the abuses laid upon the people by warring factions. Unfortunately, it's let down by the hurried voice acting and the fact that you don't actually see anyone getting screwed over by the APR's bid to blow up a dentist's nitrogen tanks or whatever.
As for funnier games? Portal and the Monkey Island games are both expertly written and hilarious.
As for funnier games? Portal and the Monkey Island games are both expertly written and hilarious.