One star ratings are ridiculous for a game of this quality. The graphics are superb, the gameplay is improved and smoother than the original. The variety of gameplay is also excellent, ranging from standard stealth gameplay to straight third person action, to fist fights between important characters, to stealth boss battles, to fighting a new type of infected in a straight boss battle etc.etc.
The visual environments are also absolutely superb, taking you across balance beams on skyscrapers, through jungle style terrain, and the more familar cities, then a sort of Floridian mansion style setting. I cannot see how anyone can really complain about these elements as given that they are such an important part of the gaming experience, a score below three stars is extremely difficult for me to understand.
The tiniest and most vague spoilers may follow.
While it's understandable that people are annoyed about the story, this is a story about hatred, grief, loss, and coming to terms with those emotions. The character motivations are almost perfectly expressed by excellent acting and a script that makes sense. Personally, this was the only logical follow on from the original that kept the post-apocalyptic nihilism of the first game. This is instantly joined my top ten list for narrative based, solo games.
Presently it's 10/10 though it could drop to a 9 on reflection, but there is no way it can possibly go any lower than an 8 for me.