1)Comparing things to Nazi Germany is a tactic that lowers any statement's credibility- I highly suggest avoiding that in the future
2)The Romans brought with them inventions, organization, and a number of innovations in a massive number of fields. This makes them somewhat more sympathetic
3)The shock of more modern empires like Nazi Germany was the modern time period and the dissonance between contemporary values and savage actions. The ancient empires were a lot more willing to use brutal tactics on the whole, so the time period leads to much lower standards and expectations for a given state.
4)People really don't think of them as great. Smart? Perhaps, though not as smart as the Greeks in the eyes of many. But great? That would be an unpopular view, at least where I'm from- people tend to regard the Romans as brutal, invasive, violent, authoritarian, and corrupt belligerents who did great things on accident from what I've seen.
