For me is Hitman Absolution - when it was coming out I was buttmad like most Hitman fans because it looked like it was more of an action game than ever before, and they ruined the disguising with the Instinct mechanic which really worked only if you played the game on Easy. I played it a bit and ditched. But a few years passed and I gave it another try and turned out that it can actually be played with true stealth, it was just harder than before. I would rate it as solid 8/10. For me the highlight was the visuals, on PC on Ultra the game looked amazing.
Honorable mentions: Fallout 3 and New Vegas, Dirt3
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Deus Ex (2000) - a game that pushes the boundaries of what the video game medium is capable of to a degree unmatched to this very day.