Uncharted, because it has everything I want in a game, such as story, a plot & characters that appeal to me, exploration, good game-play with shooting & a good cover system that enhances the game-play, and the occasional climbing & platforming that seems natural and not forced. The endings are often blah, but no game is perfect.
I know that Uncharted is largely a clone of many other different games (Tomb Raider, Gears of War, etc)....but it all comes together in a way that I like and the overall game is just very appealing to me. I like the character of Drake. I like exploring old tombs & whatnot. I like the 3rd-person shooting & cover system. I like the freedom to explore the environments. I like the use of mystery. I like the hunting for treasure or a mysterious fable. etc.
Heavy Rain would be second, because I like me a good mystery, and even though it has some plot-holes, it still tells a good story. And the graphics look stunning.
God of War Ascension. Long and very well done storyline (doesn't stray from what the original trilogy set in place, but still explores a human side to Kratos) with amazing, consistent graphics, fluid gameplay, and new mechanics to change up the pace.
Multiplayer is becoming less and less enjoyable, but I didn't buy it for the MP anyways.
PSN ID: Troll_Face_Flame (formerly armyflame) X360 gamertag: ArmyFlame9 The more people post on GameFaqs, the more I lose faith in humanity.
Metal Gear Solid 4 (as long as you count that as exclusive, I guess I do since it is console exclusive and the mobile version has very different gameplay anyway and is more of a remake). Great visuals and story, I'm a big fan of games that let you play through them multiple ways as this does (stealth is the traditional way, but you can totally play and beat this game as a shooter), some of the most exciting set-pieces of any game this gen, and I think it is up there with Bioshock as the best games of this gen, exclusive or not.