I feel like the only person who didn't like this game simply because of what it is.
Don't get me wrong, the game is well made with the exception the cinematic kill animations being way too fast. There's so many different ways to go about an objective that you could do something different every time, which is a strong point in its favour. But there's just not a lot to hook a player into continuing with the game other than the gameplay itself. The story is mind-numbingly slow and cliched, which quickly makes it boring, and the characters involved in it are mostly pointless and uninteresting. There's little to no introduction to the world and those who inhabit it before you're thrown into the focus of the game, which you NEED in a game based in a world that is not our own, and especially when the key focus is assassination. You need it in order to feel like you're accomplishing something. Instead, you're simply told there's a plague, you watch the empress die (and are subsequently framed), and then it's off to meet the ragtag group of rebels who will aid you in your vengeance (by doing nothing other than talking). Oh and there's also this dead guy who gives you incredibly useful magical abilities and a weird heart relic that lets you hear hints about the world around you, and leads you to collectibles.
Also, i've never been more annoyed at hearing my character's name. Every fifth word out of anybody's mouth is "Corvo", it's even the FIRST WORD SPOKEN IN THE GAME! Play from the introduction up until you rendezvous with the resistance, and count how many times they say that name. It's nuts.
Rather than being eased into the situation and allowing the player to develop a desire to continue, we're thrown into a foreign world and told to "get your revenge". It doesn't make me want to fight my way through a corrupt political system and return the rightful heir to the throne, I'm just killing random bad guys or sneaking around them. 2/5 stars.