I'll split into different departments as apart from Oblivion & Yakuza 3 no one game has actually surpassed my expectations on all levels as I knew my most hyped ones were gonna be amazing:
Graphics -- Uncharted 2
Gameplay -- MGS4 & FFXIII....both made a departure from the usual and both had the best combat systems in their respective franchises....this was a true surprise as especially FFXIII's paradigm system sounded like a gimmick when revealed, but it worked so amazingly! Didn't expect that much from the gameplay of both those beloved games of mine....but in the end its the gameplay of those games that made them shine the most for me, not their story shockingly. (more in FF13's case than MGS4)
Content -- Elder Scrolls IV: Oblivion, Yakuza 3, LittleBigPlanet
Story -- DQV (expected a cliched boring JRPG story...got a charming, epic and a wonderful Tale), Shin Megami Tense Devil Survivor (WOW at the story....after the boring Persona 4 I was afraid of going into it but it was so better sotrywise than Persona and amazed me a lot in that department)
Others are Super Mario Galaxy (sunshine was bad wasn't expecting much), Phoenix Wright Series (Can I say WOW...expected boring anime type game got a all round excellent game) on DS
