I'd agree with everyone else in saying Uncharted. That series is THE reason to get a PS3 (heck, with the Vita out, its the reason to get a Vita too).
Outside of that, I'd say LittleBigPlanet is a must, especially if you want a fun coop game to play with your wife. Another game that doesn't get enough publicity due to its age is Braid. It really is one heck of a game.
Also check out Deus Ex: Human Revolution. It really is a tremendous game that does honor to the first Deus Ex game. Due to its open nature, it allows you to play it in many different ways (stealth, full on guns blazing, etc....).