Those parameters are really silly, why are you are using the foundation of Rome (the city) and the capture of Constantinople (capital of an empire that had long lost Rome) as the markers for the begining and end of an empire? Could the kingdom, the republic and the empire really constitute the same entity? Nevermind the whole byzantine/roman debate. Going by that logic then from the rule of Qin Shi Huang, to the current president Xi Jingping it's been 2259 years, making it the longest lasting state in history (and continuing). After all, China is China and has remained Chinese, under the communists, under the manchurians and under the Mongols.