While you're waiting for other answers, you might enjoy these relevant posts:

• How much of an "empire" was the Holy Roman Empire? feat. /u/Aethelric

• Why is the Holy Roman Empire sometimes called "not Holy, not Roman, and not an Empire"? feat. /u/Cheimon

• What's behind the joke "the Holy Roman Empire was neither holy, nor Roman, nor an Empire"? feat. /u/kieslowskifan and /u/skadefryd. There's also a comment in that thread by /u/Searocksandtrees that links to other relevant posts.

I hope that helps!

Depends on your definition of an empire. They often have this debate about strong cultures of the past.

My definition is that the top figure is "a king of kings" or the Homeric term "a great king." What does that mean? It means that a ruler has client kings under him. Britain used to have kings under the king but they started calling them Earls.

I would actually classify HRE as an Empire since it had a system of princes/electors.

Some academics define an empire in terms of how great the roads were, the common language, the common religion.

It just depends on your school of thought on what makes an empire.