only God can create.
only God is able to create.
I'm a native speaker and it is very very uncommon to use the word "is/are able" over the word "can". It is grammatically correct but is abnormal, so my recommendation would be to use the word "can". The sentence "Only God can create." sounds a lot better because that is how people talk. People understand that the context isn't that someone gave God permission to create but that it is an ability which only he can do, it is also implied in the sentence.