I think that Bulls team was the best one LeBron has faced in the East during this run.
Even then, the Bulls lacked dangerous scorers aside from Rose. Still, that was a decent accomplishment.
As for beating a 56 win Celts team in 2011, I'm going to assume you havent forgotten that Shaq couldn't play and Rondo dislocated his elbow during that series.
The Celts the next year were a last gasp team that probably would have been run off the floor by OKC had they made it past the Heat.
The Pacers, Hawks, and Raptors don't impress me. Solidly second tier teams that dominated weaker opponents in the regular season with depth and balance. Not a threat to go far. Not teams we will be talking about years later in terms of what they were able to accomplish.
Its a far cry from 2008 when you had the new Big Three Celts, the Cavs, Dwight's Magic, and the former champion Pistons.