So which is greater, a team that wins the championship by going 4-3, 4-3, 4-3, and 4-3, or a team that loses the championship going 4-0, 4-0, 4-0, 3-4. Team 1 - 16-12 (.571) Team 2 - 15-4 (.789).
What matters most is this stat - Bill Russell - 11 titles, 13 years (.846). Most titles, and one of the highest percentages.
The ultimate goal is the championship, so the ultimate measure of success is the measure of your consistency in achieving that ultimate goal.