Originally posted by: Horus
Romans, definately. They had an empire spanning from the British Isles to deep into the Middle east, and into Africa as well. It was an empire that lasted for centuries as well, even up until the 19th century with the Holy Roman Empire.
Founding of Rome supposedly around 700BC, fall of Byzantium in 1453AD. That's ~2150 years from founding to the end.
Egypt: 3300BC to 300BC, 3000 years. And that's taking the Roman Empire as meaning "from the founding of Rome when it wasn't an Empire" and Egypt from founding to the end when it was conquered by the Greeks. They both lasted pretty long.
Egypt had a few falls and divisions along the way, but Rome wasn't an empire until 31BC, and din't have it all good even once it was an Empire.
In terms of lasting effect Rome could be seen to have had a greater impact, they brought Christianity to the forefront of religion, along with numerous technological things which kinda went away then came back later, but then again the Egyptians and Greeks influenced the Romans, and Egypt had monotheism pretty early on for a short time, and most of the developments which helped Rome came from elsewhere, and a lot from the near east, even if it wasn't from the Egyptians.
So it's a tough call and can't really be done with a vague question like "who had the best empire" as they both had the best in some respects, but not others, they came at different times, and they can't really be compared in that kind of way, IMO.