I think that John Browning was the greatest firearms designer/ inventor for one simple reason. He had to pioneer almost everything he invented. He had very little past history to look back upon and study, to see what has worked in the past and what hasn't. Kalashnikov, Stoner, Bill Ruger, Glock, all of those poeple had a long history of firearms design to study and look at, before proceeding with their work.
Kalashnikov could look at Garand's design and study it, like wise with the STG 44, and Walthers' attempt at an automatic rifle, not to mention earlier Swedish and Mexican (Mondragon) designs.
Stoner had the Swedish Ljungman (hope I spelled that right but I bet I didn't)and Egyptian Hakim designs to study.
When Bill Ruger came out with his bolt actions and his #1 they were more refinements and modifications to existing designs than groundbreaking now designs. People had been making bolt actions and single shot rifles for decades, and Mr. Ruger could look back on those guns and study what worked and what didn't and he knew before what he started what NOT to put into his designs. That is why Ruger bolt guns don't cock on closing and have 1891 Mauser type extractors.
In summary, I don't think we will ever have another John Browning among us, and that is too bad....