its not all its cracked up to be

Its not all its cracked up to be is another way of saying that something is disappointing and that it does not live up to its reputation. This phrase is usually in reference to something that has a certain reputation where people talk about how great and wonderful it is, when in fact it is nowhere near that good. When something isnt all its cracked up to be, it means people boast about it but it doesnt deserve to be boasted about.