It totally depends on what data is being stored in the option, maybe_serialize will determine in the option is holding a singular static value, such as true/false, 0/1, empty string, whatever(it’s called when an option is created or updated).. it will serialize when dealing with objects and arrays, singular values are not serialized.
The get_option function is equipped to deal with this however and will unserialize(or not) as necessary for you(using maybe_unserialize) when it’s called, which basically does the inverse of maybe_serialize.
Hope that helps..
EDIT: Confirmed – checked source, above information is correct regarding serialization.