Resident Evil 4

Survival horror game from Capcom. Played on Nintendo Gamecube, also available on PS2 and Nintendo Wii.
The game that radically changed the survival horror genre. While not actually as scary as previous Resident Evil games, it succeeds in making the series far more dynamic and vastly improves the gameplay. Aiming is done from a semi-first person over-the-shoulder perspective using a laser sight, so lining up headshots is far more skillful than before. Essentially still a survival horror, you have to think carefully about how you spend your ammunition. You now have to also think about how you spend cash as weapons can be upgraded, but this is costly; will you really be using that mine thrower that much, or should upgrading the shotgun's capacity or firepower take priority? The merchant who sells weapons and offers upgrades is also so brilliant, he alone bumps this game up to 8/10
AI is also much improved over zombies, as the villager enemies work in groups to attack you or kidnap your companion Ashleigh. Ashleigh, while annoying, is thankfully considerably more intelligent than that mentally challenged woman in Ico. It can be irritating when she gets herself knifed though.
However any flaws are too minor to make a difference. The game is just so cinematic, you feel like you're in an action zombie movie. Quick Time Events are used a la Shenmue, to very cinematic effect; and the death scenes when you mess up are nothing short of awesome. Getting your face melted off by acid is a personal favourite, and there's even a QTE fight with multiple deaths.
In terms of lifespan, the main game is a very respectable length, and fun to replay repeatedly, plus there are bonus modes to play such as mercenaries, in which you can even play as some of the villains. I can't in good conscience give the game anything less than 10.