The Chicago Bulls were the best regular season team this year, but they got ousted from the first round of the playoffs when Derrick Rose went to the ground with a torn ACL in the first game of the postseason.
They might be the best team to miss the finals this year, but they aren't one of the 10 best teams in history to miss the finals.
Basketball-Reference has a stat "SRS" that stands for Simple Rating System. It's a strength of schedule adjusted ranking structure to power rank teams.
Here are the 10 best SRS rankings by teams in NBA history who didn't make it to the NBA Finals. I imagine some will complain that SRS doesn't mean anything, but allow me this explanation.
In order to get to the top 10, I had to go 30 teams deep. The other 20 made the finals and the majority won them.