Pretty clear it would be the Boston Celtics. Taking Rondo off the Celtics, they have a clear advantage over a league that would have lost all their premier superstar players. They'd still have scoring, size in the front court, and really good defense. Their depth at PG takes a hit because then they'd have to split time with Delonte West, Nate Robinson, and maybe Marquis Daniels at PG. But the offense can run through Pierce and KG more. They'd also simply have to be more of a half court offense. But if healthy, they would be clearly the best team in a league that doesn't have Kobe, LeBron or Wade (either one you argue), Duncan, Dirk, CP3, D12, Carmelo, Deron Williams, Rose, Nash, Roy, Joe Johnson...
Boston would win the le easily imo.