I feel that the rating should be much higher. Count how many championships Russell had in his tenure. That is why he is in the Hall of Fame. Also, count how many times he beat Wilt Chamberlain.
Bill Russell, IMHO, should be in top 5. Where I'd place him certainly can and should be debated. Take a look at my list, if you want to know where I have placed them in the respective ranking. I place him higher than Chamberlain, who I believe that you placed in the Top 5. Fact remains that Russell beat him head-to-head for quite a few of the Finals.
Where you 'should' place them on your list...is your call, of course. I, frankly, question your objectivity that you do not place Russell in the Top 5. I see that as a reflection of your youth and your not having seen much of the NBA from 1960-1985.