This is a great thread, can't believe I'm just seeing it.
GOAT Squads:
1) -2000-2002 Lakers: Shaq was nearly impossible to guard. Sure, teams started the hack-a-Shaq, but it really wasn't that effective. Add to that Kobe - who was still a top-5 player in the NBA before his prime - ensured that teams could not effectively double Shaq. Their perimeter defense with Fisher, Horry, Fox, Kobe, and others was nearly unstoppable, arguably one of the best of the given choices, and they all could make plays by themselves.
2) 2014 Spurs: This team was arguably the best on this list. Obviously Miami was at their worst in 2014; however, they were still an outstanding team. Spurs didn't care and trashed them. Green and Mills having career years made the aging of Parker and Ginobli less-noticeable. Kawhi combined with Tim Duncan, Diaw, and Splitter made the Spurs impossible to drive against. Just a very tight unit.
3a+b) 2012 and 2013 Heat: People forget how cruelly efficient Miami's offense was during their championship years. Spo installed a beautiful offense that allowed LeBron to be just as successful off-ball as on-ball. Battier is one of the smartest players in the past twenty years. Heat were holistically worse in 2013, even with the addition of Ray, but they were still damn good.
4) 2005 Spurs: Top-to-bottom the most talented Spurs roster. Ginobli, Parker, and Timmy had outstanding seasons and were flanked by other great talent. I was less impressed with their cohesion than the 2014 Spurs, nevertheless, the team was still outstanding.
5) 2004 Pistons: Arguably the best defensive team of all time. There wasn't one player in their starting five that wasn't an all-NBA defense caliber player. They showed that excellent defense and teamwork can beat any degree of talent. The 2004 Lakers, top-to-bottom, were as talented as any team we've ever seen. But they couldn't figure out how to stop a Pistons team that knew every aspect of the game backwards and forwards.
All-Time Teams:
6) 2016 Cavs: As a team, we weren't strong enough to beat any of the top-5. With that said, the sheer talent of Kyrie and LeBron makes us one of the best teams of the past two decades. If we can really stick to our core, I think the Cavs may have a Spurs like dynasty on their hands for the next six years or so. We have an aging top-3 all time talent, a lot of young, promising pieces, and a core that will age into success.
7) 2007 Spurs: It's tough to rank these guys because they only had one playoff round where they were tested. With that said, they did beat the prime-level "Seven Seconds Or Less" Suns and posted a top-5 most dominating NBA Finals performance. The team wasn't sexy, but they did everything right, and won because of it.
8) 2009-10 Lakers: These teams get no credit because they weren't as good as the Shaq-Kobe Lakers; however, that's a mistake. Oddly enough, given the talent, this squad was more likely to grind you out. Nonetheless, Kobe and Gasol gave the team two guys who could score at will. Unfortunately, top-to-bottom, they were not as talented as a lot of other aforementioned teams.
NBA Champions, But Not All-Timers:
9) 2015 Warriors: It's tough to evaluate this team because they won three straight playoff series where the other team was missing at least one starter for the majority of the time, including a finals performance where their opponent was missing two all-star starters. Nonetheless, their offense changed the game, and that is to be respected.
10) 2008 Celtics: They were one of the first, real superteams. Nonetheless, as a unit, I find them to be incredibly overrated. The 2004 Pistons did everything the 2008 Celtics did but better. Outside of creating superteams, this squad is most well-known for revitalizing the careers of three stars who had never won before.
11) 2011 Mavs: They sort of acted a precursor to the 2014 Spurs. Building off the 2004 Pistons, the 2011 Mavs showed that stifling defense, an offense that creates easy buckets, and excellent basketball IQ can lead to a championship victory over a superteam.
12) 2003 Spurs: Sure, they established San Antonio as a dynasty. And sure, their frontcourt defensive players were incredibly impressive. And finally, yes, we all know that this team showed Duncan's all-time potential. But as a unit they were just not as impressive as most teams who've won championships since 2000.
13) 2006 Heat: Outside of further emphasizing Shaq's all-time greatness and introducing us to Dwyane Wade, this team was incredibly unimpressive. Most of their squad was washed up, and at best they were a poor man's version of the 2000-02 Lakers. Riley installed an iso-heavy offense that relied on Dwyane Wade's drive-and-dish ability. This offense allowed Shaq to be successful again, and to that, the team deserves credit. The Pistons were outstanding that year, and Riley found a way to utilize Shaq against Detroit's defense, which was impressive. But the team was underwhelming as far as NBA champions go.