I don't recall Shaq saying anything about Orlando, LA, Miami, Phoenix, or Cleveland in regards to how good a team they were.
What he did do is say Kobe was the best player he ever played with when he went to LA (jab at Penny), then Wade was (haymaker at Kobe), then Nash was. I don't remember him saying it about LeBron...
But I will buy this comment. This TEAM is far better than any other one he was on. The only team that you can compare is the 2000-2002 Lakers. And without Shaq on either team, the Celtics are significantly better and deeper. Shaq MADE his LA team, he simply adds to this Boston one.
Add in the chemistry and cohesion and ease of playing for Doc, I'm sure he's genuinely happy. He looked like he was trying to look like he was having fun in Cleveland, got bored in Phoenix, and eventually hated Miami and LA.