Dishonored
Unfortunately, none of Dishonored's subsequent missions had nearly as many optional side-objectives as the first. Actually, the most disappointing thing as the game went forward (and eventually ended) was how shallow the effects of these and other choices were: usually limited to a line or two of dialog, or a bonus item when doing a favor for someone. Even the game's most dramatic choice - the amount of "chaos" you create (leaving things alive or killing them instead) - only changes the static scenes and voice-over of a brief ending sequence. So, it's actually harder than I expected to justify playing through the game more than once.
That being said, the gameplay that gets you to that ending is pretty top-notch; so if you can't enjoy it for the personalized consequences, you can at least enjoy the sneaking and assassinating for its own sake. Dishonored's levels are imaginatively and intricately crafted, with plenty of routes between you and your objective. Blink up the side of a building and sneak in a window? Possess a rat (or a guard) and find a secret route to a safe hiding spot? Stock up on potions and ammo, and storm the front door? Well, the latter option is usually unreasonably difficult, but otherwise the level of freedom is refreshing.
Dishonored's levels consistently feel like wide open worlds to explore and exploit as you see fit. (Actually, another of my complaints is that too many collectibles - runes and charms for special powers, and item/money caches - are way, way far off the beaten path.) Every blocked door, guarded hall, and swarm of enemies is a puzzle with multiple solutions, an opportunity to try new approaches and discover more about how the game works.
The story and setting is pretty good, too, aside from some uneven voice acting -- particularly Piero, who sounds like he's channeling the lowlights of PlayStation 1-era voicework. And despite a genuinely cool twist, the final levels can feel like they're dragging on a bit too long. But -- don't let my constant descent into gripes distract you from what is, overall, a fantastically entertaining and compelling game. It's imperfect, but there's plenty of good stuff in here.
Better than: BioShock 2
Not as good as: The Elder Scrolls V: Skyrim
Maybe as good as: BioShock, Batman: Arkham Asylum
Progress: Finished with high chaos