Before they were all put together, KG was the best PF in the game, Allen was one of the best SG's in the game, and Pierce was one of the best SF
They got put together to make a great team, and everyone likes watching them.
If there was a team with 5 superstars, everyone would like watching them, and for that matter, rooting against them.
Heres one for you, changing sports, Barcelona. Some people say they just started buying the best players in soccer, and yet they lost, but were fun to watch.
I'm not the kind of person that likes watching a team just because they are good, however, it would be interesting to see what a superstar team in the NBA would do. I'm a Hawks fan, and they don't really have one superstar. Any game, any player out of their key 6 can be dominant, but none are considered a superstar, and yet, I watched probably 30 of their games this past season.