The Imperial class is the only one besides the Tector have that class name. The rest are not the same for example the Victory (900 meters) is really a heavy cruiser if you go by the Anaxes War College, nor is the Gladiator (500 meters), that a cruiser class

• Corvettes: Ships of roughly 100 - 200 meters length
  • Example: CR90 corvette, Marauder-class corvette
• Frigates: Ships of roughly 200 - 400 meters length
  • Example: Corona-class frigate, EF76 Nebulon-B escort frigate
• Cruisers: Ships of roughly 400 - 600 meters length
  • Example: Belarus-class medium cruiser, Broadside-class cruiser kdb-1
• Heavy Cruisers: Ships of roughly 600 - 1000 meters length
  • Example: Acclamator-class assault ship, Dreadnaught-class heavy cruiser
• Star Destroyers: Ships of roughly 1000 - 2000 meters length
  • Example: Imperial-class Star Destroyer, Nebula-class Star Destroyer
• Battlecruisers: Ships of roughly 2000 - 5000 meters length (small battlecruiser models were classed as "Star Cruisers", to separate them from larger ships of the type, but few recognized this classification as a formal part of the system.)^[1]
  • Example: Bulwark-class battle cruiser, Praetor Mark II-class battlecruiser
• Dreadnaughts: All ships over 5000 meters length
  • Example: Executor-class Star Dreadnought, Kor Chokk grand cruiser

(Yes I got this from the Wiki....I don't own any of the material.....blah blah blah)

Thoughts?

MC 80 are classed as "Star Cruisers"

destroyer are a type of vessle of war just like a sloop of war or bird of pray

venator is a star destroyer made to counter massive swarm of droid fighters aka a fleet carrier

victory was made to fly in strike/raid fleets aka a cruiser

ISD was made to for captial ship to capital ship combat aka a battleship

in star wars battlecrusers are lager than battleship contra RL

battleship is a star cruiser that are in the gray area think german ww2 pocket battleship

Since the rating system was no longer a reliable indicator of a ship's combat power, it was abolished together with it the classifications of sloops, corvettes, and frigates. Instead a classification based on the intended role of the ship became common, such as cruiser and battleship

Well, I seem to remember from a yesteryear edition of the Star Wars Role Playing Game that the designation "Star Destroyer" referred to a series of related designs rather than an actual classification of warship.

The great thing about Star Wars though is there is always a relatively intelligent writer out there capable of explaining away something from the movies or other publications which would make you scratch your head if you thought about it for a second or two.

The term doesnt come from a Destroyer in the naval term, but Star Destroyer that is a ship able to attack a star system, coz it have hypedrive, big guns, troops.
http://starwars.wikia.com/wiki/Star_Destroyer/Legends

"The term originated with the idea of a warship powerful enough to destroy entire star systems, and did not necessarily indicate a destroyer type vessel"