One of the things that made Roger Ebert such a good reviewer at his peak (not talking about his later years when he seemed to like everything and let his personal politics cloud his writing) was that he would measure a movie essentially against what it was trying to be. Lethal Weapon and Ordinary People weren’t trying the same things so pretending that 3.5 star ratings for them meant the same thing was silly.
I expect very different experiences from a Paul Thomas Anderson movie to a Marvel Universe movie. So, just an aggregate of 81 percent doesn’t mean all that much.
Definitely, he was one of the few reviewer to actually “get” exploitation movies. He could understand that sure the plot’s stupid, but it’s executed well. Especially in that time frame when most reviewers were basically trying to be auteurs and were really pushing arthouse, Ebert’s ability to appreciate a good car chase really separated him from the crowd.