I've been to Brugge three times and I'm yet to be disappointed.
I know we are all different but I really struggle to see how people rate Brugge at three stars. It's a 5 star tourist destination. One of the best preserved medieval towns in Europe, the "Venice of the north" with it's extensive canal network (although I dislike that tag) and several UNESCO listed sites besides the Historic Center of Brugge itself.
Yes, it does get overrun with tourists (what do you expect?) and it can be expensive but it's still one of the great sights in Europe and definitely the best in Belgium.
The centerpiece of the town is the Grote Markt (market square) with the towering 13th century Belfort (belfry of Brugge, also part of a UNESCO listing, Belfries of France and Belgium) looming over it. The square itself is surrounded by beautiful Flemish houses with their stepped facades.
But there is more to Brugge than the fairy tale main square. There's another UNESCO site to the south of city center, the Begjinhof (Flemish Béguinages), that sits at the north end of Minnewater Park (picture), a lush open green park surrounded by canals and dotted with medieval fortifications. There's the impressive Sashuis (lock keepers house) where the waters of the canals flow through the arches that support the main building.
Other notable sights include the Burg and the Basilica of the Holy Blood. 
Despite the many sites though, the joy of Brugge is actually just being there, wandering the narrow cobbled streets and navigating the bridges that criss-cross the canal network. 
On a cold winters day, go and enjoy a Kwak beer at one of the many charming pubs to found around the square, take care though, at 8.4% it's not to be taken lightly. Then brave the cold cobbles of the square and buy a portion of frits and mayonnaise and marvel at the bell tower.To be honest, I would rank it as one the of unmissable sights of the world.