I have three options:
1.Tang dynasty. Most Chinese agree with this answer. We always think that's the most splendid period of chinese history. We were the richest, the most adwanced, the most openminded.（Oh, really?） Many chinese communities are also called Tangrenjie(Chinatown).
2.The Three Kingdoms period. I heard from a Japanese saying that the first dynasty of China he knew was the Three Kingdoms period cause he played some computer game with this background. I also heard that some university in America opened a selected course, teaching the students how the Sanguo-culture influenced Chinese. They also play the popular board game "War within three kingdoms". What a shock!
3.Qin dynasty. It's said that the big china was united in Qin dynasty for the first time. And the Qin Emperor has many fans.
Do you have other answers?