The current amount of importance placed on "originality" is a fairly recent phenomenon which I will discuss at some point. Back in the day, by which I mean Roman antiquity, imitation was indeed the sincerest form of flattery. Thank goodness, too. Because the Romans admired the Greek aesthetic, talented artists spent a great deal of time creating hand-made replicas of notable Greek art, particularly sculpture. In some cases, the originals are now lost to time, and the only reason we know what they look like is because of the talented copyists of old.
Perhaps the best-known example is the Diskobolos by Myron. The bronze original was remarkable enough to be discussed by a number of ancient playwrights and historians who saw it first-hand, but what a shame it would be if their descriptions were all we had to go by.