they haven't been consistently good since the 80's (and then they weren't dominant by any stretch). Since 1996 we have now been to the 2nd round of the playoffs twice (this year and 2009).
The Broncos will always be the biggest game in town. People bleed orange in Denver. That being said if the Nuggets can stay consistently good (and the future looks bright) I think they will have plenty of great fans.
You are right in that Jokic is extremely likable. He is kind of a happy go lucky goofball who just happens to be really, really good at basketball.