That was always the goal of salary caps wasn't it? Enforced league-wide mediocrity? At least that's what I remember seeing around here the last time I paid any attention to da foozeball.
In the late 90s, it felt different. Teams weren't really historically outstanding like the Patriots of today (save for maybe the '99 Rams and their insane offense), but you had a lot of really good teams that put themselves in legitimate Super Bowl contention. Within a span of four seasons ('97-00), the Jags, Ravens, Colts, Titans, Jets, Broncos, Chiefs, Steelers, Packers, Rams, Bucs, 49ers, Falcons, Vikings, and Giants all put together credible runs where you could have seen any of them bring home a Super Bowl without tilting your head sideways. That's about half the league.
Nowadays you can pick out about three teams by midseason and almost guarantee that the Super Bowl winner will come from that group. The rest of the league just occupies a vortex of mediocrity.