there are around 3 review sites that I trust...Eurogamer is one of them...they give Thief a 6/10...
"Thief is a frustrating game as much as it is a disappointing one. There are glimmers of what could have been: the exquisite concept art used in the loading screens shows the care and attention that's gone into conceptualising this dim-lit world...At times the game suffers from a lack of ambition, placing far too much importance on the tiresome looting of endless cupboards and dressers in the vain hope that this will be enough to propel you forwards. In other places, Thief suffers from too much ambition, unable to draw its systems into a cohesive whole. Whether the game simply needed more time or entirely different foundations is never quite clear. Either way, it's a game that adds up to less than the sum of its parts. Undeniably, Thief suffers greatly by comparison to Dishonored...
http://www.eurogamer.net/articles/2014-02-24-thief-review
"Thief is a frustrating game as much as it is a disappointing one. There are glimmers of what could have been: the exquisite concept art used in the loading screens shows the care and attention that's gone into conceptualising this dim-lit world...At times the game suffers from a lack of ambition, placing far too much importance on the tiresome looting of endless cupboards and dressers in the vain hope that this will be enough to propel you forwards. In other places, Thief suffers from too much ambition, unable to draw its systems into a cohesive whole. Whether the game simply needed more time or entirely different foundations is never quite clear. Either way, it's a game that adds up to less than the sum of its parts. Undeniably, Thief suffers greatly by comparison to Dishonored...
http://www.eurogamer.net/articles/2014-02-24-thief-review