Yes, he was amazing. So much of the music is either directly his arrangements or was shaped by his suggested instrumentation.
He also had an amazing ability to interpret their sonic needs. When John would say something like, "I want it to sound like a thousand chanting tibetan monks," he (along with engineers like Geoff Emerick) would have to figure out how to do that...? -He would end up running Lennon's vocals through a twin Leslie speaker and we get:
You can read more about the ingenuity that went in to that song. They weren't just making music, they were literally creating new ways of recording music that is still used or emulated today. -check out the "recording" section.
So fucking cool. The best producers/engineers are perfectionists, musicians, but they're also interpreters. Many musicians/songwriters are fucking crazy, difficult personalities that will say things like, "it's too busy" and give little other direction, it's then up to the producer to read between the lines and figure out what the fuck that means. By all accounts Martin was amazing at this. He was also amazing at keeping the largest ego in music in check. John was no picnic -For example, when the Leslie speaker was introduced as an idea for making him sound like those monks, he suggested they could get the same effect by suspending himself from the ceiling by roper and spinning him around the microphone. Good thing George/Geoff went with the Leslie. Somehow Martin kept those guys all productive even after the death of Brian Epstein. His contribution to music cannot be overstated imo.
You are right about the measure of a person and the world is way better off for having him here. He kicked ass.