They were replaced by Republics.

We have met the enemy, and he is us — Pogo

I assume so, but now that I check I can not find a good source for it. As the German Empire discussed in Frankfurt did not seem to make a distinction on Roman heritage between the small German and big German solutions, I tend to view it as they (and later the German Empire of 1871) saw emperor as the proper title for the head of the German states, in accordance with the tradition of the Holy Roman Empire. German Empire and Austrain Empire as successor states (albeit with a delay) of Holy Roman Empire (dissolved by Napoleon in 1806 (another roman emperor)).

On small vs. big Germany:
German Confederation - Wikipedia, the free encyclopedia

On May 18 the Frankfurt Parliament opened its first session, with delegates from various German states. It was immediately divided between those favoring a kleindeutsche (small German) or grossdeutsche (greater German) solution. The former favored offering the imperial crown to Prussia. The latter favored the Habsburg crown in Vienna, which would integrate Austria proper and Bohemia (but not Hungary) into the new Germany.

An interesting piece on the title of German Emperor:

William I, German Emperor - Wikipedia, the free encyclopedia

The title "German Emperor" was carefully chosen by Bismarck after discussion until (and after) the day of the proclamation. William accepted this title grudgingly as he would have preferred "Emperor of Germany" which, however, was unacceptable to the federated monarchs, and would also have signalled a claim to lands outside of his reign (Austria, Switzerland, Luxemburg etc.). The title "Emperor of the Germans", as proposed in 1848, was ruled out from the start anyway, as he considered himself chosen "by the grace of God", not by the people as in a democratic republic.

But then William I also had a full title:

William I, German Emperor - Wikipedia, the free encyclopedia

His Imperial and Royal Majesty William the First, by the Grace of God, German Emperor and King of Prussia, Margrave of Brandenburg, Burgrave of Nuremberg, Count of Hohenzollern, Duke of Silesia and of the County of Glatz, Grand Duke of the Lower Rhine and of Posen, Duke in Saxony, of Angria, of Westphalia, of Pomerania and of Lunenburg, Duke of Schleswig, of Holstein and of Krossen, Duke of Magdeburg, of Brene, of Guelderland and of Jülich, Cleves and Berg, Duke of the Wends and the Kassubes, of Lauenburg and of Mecklenburg, Landgrave of Hesse and in Thuringia, Margrave of Upper and Lower Lusatia, Prince of Orange, of Rugen, of East Friesland, of Paderborn and of Pyrmont, Prince of Halberstadt, of Münster, of Minden, of Osnabrück, of Hildersheim, of Verden, of Kammin, of Fulda, of Nassau and of Moess, Princely Count of Henneberg, Count of the Mark, of Ravensburg, of Hohenstein, of Tecklenburg and of Lingen, Count of Mansfield, of Sigmaringen and of Veringen, Lord of Frankfurt, etc.

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