I'm severely disappointed by the ending to almost every video game I've ever played. It's like they're just tacked on for when the action is over; it sucks ass.
Among the very few video game endings that I actually liked were those to Knights of the Old Republic, every Half-Life game (except Episode 1, which underwhelmed me generally the first time I played it, though I did appreciate it more the second time through, and Blue Shift, which seemed truncated rather than ended), and FEAR.
Some of the "afterthought" endings that left me with a particularly foul taste in my mouth were to American McGee's Alice, Giants: Citizen Kabuto, Armed and Dangerous, Brothers in Arms, Halo 2 (I love a good cliffhanger ending, but this was a really, really bad cliffhanger ending), and Indigo Prophecy.
Seriously, it seems like every game ending is designed either to start or continue a franchise, or is just tacked on without any real thought. Either way, they're very rarely satisfying at all.