When I try to do a building it never looks like a real building- it just looks like a child has built it out of building blocks!
Can I make a suggestion Nat?
Do what I do. Look at some of the really good builders (look in the workshop) and find a building you like. Now try and see (or download a blueprint from the workshop) and pull it to bits to see how its been created.
Also look at some videos from some good builders. A great tip that Geekism made in one of his videos is to ensure that you have something filling large areas (of walls or roof space). Look at real buildings - you don't tend to see large areas of (say) brickwork, without anything breaking up the space. This is particularly true in a real theme park.
When I was lucky enough to visit some theme parks in Florida, it amazed me that no matter where you looked (or could see), it was themed. There were no areas where they couldn't be bothered, even around the back of service areas, there was theming.