Benchmark navies are more useful than greatest-navy rankings

Was the Royal Navy the greatest navy in history?

It is better described as the benchmark navy for a long era, just as Spanish, French, and now American naval power supplied the comparison point in other periods.

The Royal Navy has a strong claim to historical greatness, although that category is too subjective to settle. A more precise question asks which navy served as the period's benchmark, the force whose ships, doctrine, and power everyone else used for comparison. The Spanish and French navies held that position in some eras, the Royal Navy did so for a long period, and the United States Navy does so today. This framing makes comparative naval power historically specific rather than turning it into a timeless league table.