Alright, let's do this!
Russell's best seasons:
1962
1965
1963
1964
1960
1966
1961
1959
Wilt's best seasons:
1967
1964
1968
1962
1965
1966
1963
1960
My list:
1. 1967 Wilt Chamberlain - very strong candidate for GOAT individual season, very rare combination of offensive and defensive impact. Russell peaked higher on defensive end, but he can't match Wilt's two-way exellence.
2. 1964 Wilt Chamberlain - I've thought quite a bit about this one and I'm not 100% sure with this choice. Wilt carried his roster heavily, more than Russell ever did. He had one of his finest defensive seasons in that year despite massive offensive load. Again, I prefer two-way impact of Chamberlain over Russell's GOAT defense.
3. 1962 Bill Russell - Russell's best offensive season and one of his best defensive seasons as well. He arguably outplayed Wilt h2h in the playoffs and had spectacular finals series. Can't take any other Wilt season over that one.
4. 1965 Bill Russell - 1968 Wilt peaked higher in RS than Russell, but his injury made his performance less complete overall.
5. 1963 Bill Russell - quite close to his 1962 self, slightly worse offensively though.
6. 1968 Wilt Chamberlain - a close battle between this and 1964 from Russell. Russell's offensive struggles in playoffs were bigger than Wilt's in my opinion and that's the key factor here.
7. 1964 Bill Russell - people don't realize how incredible 1964 Russell was - he played with relatively weak team around him and carried them through strong competition with relative ease. I could see it even higher, but it was one of his weakest offensive season from his prime. He clearly needed a time to adjust after Cousy's retirement.
8. 1960 Bill Russell - solid offensive season from Russell, though Odinn pointed out some turnovers problems in postseason. That said, it's more complete season than any of Wilt's seasons left. He also outplayed rookie Wilt h2h in playoffs, which is additional point.
9. 1962 Wilt Chamberlain - very strong RS backed up by highly underrated postseason performance.
10. 1966 Bill Russell - he struggled with injuries a little bit, but it was still very solid season nonetheless.
11. 1961 Bill Russell - relatively weak RS from Russell, but better than 1965 Wilt.
12. 1965 Wilt Chamberlain - outstanding playoffs performance, but mediocre RS due to heart problems.
HM: 1959 Russell and 1966 Wilt.
I expect long discussion in this thread and I can't wait to see more opinions.