Broncos run of sustained relevance is very strong, but the Steelers have had similar success over the last 30 years, and if you include the 70's they blow the Broncos out of the water. The Broncos have gotten to the Super Bowl more often recently though.
Since 84
4 AFC Titles
2 Super Bowl Titles
13 Division Titles
Current streak of 12 seasons without a losing record.
7 losing seasons
Overall
6 Super Bowl Titles
Best Record since NFL/AFL Merger