I think DM2 was an awesome movie, but I've always been a sucker for Jackie's older movies. Most are pretty corny/horrible, but Jackie is so cyoote in them. ^^ One of the few exceptions is the first DM. I especially agree with what was said earlier: If someone were to go back in time and give a younger Jackie chan the brains and experience of his current self, we'd see some pretty amazing stuff.
I forget where I read it, but I remember it being reported on a very credible news site (CNN, Fox or something similar) that Jackie was actually supposed to be filming a scene on the WTC for his next film on September 11th, but it was canceled due to a delay on the script. o_o
Anyways, I dunno if I'd call it his "prime", but some of my most favorite Jackie Chan films are the romances like Rumble in the Bronx and Cityhunter.