Fictional spaceships are often unique in many ways, including their size, capabilities, and history:
Size
Some fictional spaceships are city-sized.
Capabilities
Some fictional spaceships have unique capabilities, like cloaking technology, faster-than-light travel, or the ability to travel through time.
History
Some fictional spaceships have an impressive history, like the USS Enterprise.
Adaptability
Some fictional spaceships are adaptable and can be used for multiple purposes, like the Millennium Falcon, which was originally a light freighter but was modified for smuggling.
Design
Some fictional spaceships have distinctive designs, like the SSV Normandy's sleek and streamlined shape, or the Millennium Falcon's circular body and two spikes pointing ahead.
Crew
Some fictional spaceships have famous crews, like the Millennium Falcon's Han Solo and Chewbacca.