Just watched Force Awakens, and don't see how it is 2.2 points higher
Force Awakens is just a hodge podge of ESB and ANH. It didn't take any big chances like TPM. It's a decent movie, but nothing in the high 8 range. Phantom Menace tries to show the scope of the Star Wars galaxy. It is an expanded view of what Star Wars is from Lucas. A time of peace before a great war, started by internal machinations. If you can take out all the purposely cheesy "battle droids" and take Jar Jar for the hapless idiotic hero that he is, it's got a lot going for it.
I think in general the prequels are underrated. JJ just took the original movies that everyone liked and aged the core characters. Lucas had to make a backstory for everyone in the original trilogy, and introduced all types of new ancestor characters. Sure, peacetime Jedi sitting around aren't too exciting to watch, but TPM is all about the Jedi becoming complacent, and not seeing a threat rising right underneath them.