I look at Octagonal and think he was quite underrated compared to Lonhro. Maybe not a top 10 horse but should be on the very outskirts.
Octagonal won a G1 as a 2yo and 2nd in 2 others including the Slipper. Won the Cox Plate as a 3yo, after being placed in the Caulfield Guineas, 3yo triple crown in Sydney plus the BMW. Had a shocker of a spring as a 4yo and then managed to win a few more G1s in the Autumn.
He raced against a 3yo crop of Saintly, Filante, Nothin Leica Dane, Flying Spur, Our Maizcay and a few others who were very competitive against the older horses. I caught all of his 3yo and 4yo races in Sydney and I rate them highly. My favourite would have been Dye taking off in the Chipping Norton at the farm and beating Juggler.
There are others in the list like Saintly and Beau Zam who injury free or better ridden would have been even higher.
Beau Zam had some terrible luck or rides in his 3yo spring. I still remember him as a kid coming 2nd in the CC, 5th in the Cox Plate and 7th in the Derby to his stablemate Omnicorp.
Schillachi was another if retired early would have been near the top but the latter years took his gloss away.
What about Mahogany who managed to win Derbies, Guineas, G1 races as 2yo and fitted in a couple of Lightning races too.
We sometimes put too many horses who win for a year or two in greats or champions when there maybe horses who won the same number of G1s but fell away in the latter part of their career as age does catch up.