I can write a 3,000 word essay on why both Bradman and Sobers are nowhere near as great as they are made out to be, and it is the propaganda of the cricket establishment to give them the greatest-of-all-time batsman and A/R title, but for the sake of brevity, I shall add my two cents as briefly as possible.
I will not argue over why Bradman is not the best batsman to walk the earth, because that is difficult to do so consider cricket was a completely different sport in his time. We are not talking about the 90s, 80 and even 70s here; we are talking about the 1930s.
One common argument that I often here is he is the best ever because no other batsman has been so far ahead of his peers. No doubt that's true, but why must we assume that his level of competition was great?
Why is not possible that he was lucky to be a great player in an era of decent to average to awful players? Would he still be the clear number one if his competition was Tendulkar, Richards, Lara, Ponting, Kohli etc.?
The major fallacy in this no one else has been so much better than his competition argument is the convenience to keep the level of competition across eras constant.
It might be true that he is the greatest genius of all time and his peers were also great but he made them look mediocre, or it could also be true that his competition was not great. The point is that we do not know, and thus we cannot say that he is undisputedly the best of all time.
Bradman with his 1930s technique would be a number 11 today, but I won't argue technique. It is a product of time and if Bradman lived today, he would have had a different technique and would have still been a quality player. However, the reverse is also true. The contemporary greats would still have been greats had the played in Bradman's era and it is possible that they would have a similar average if one considers the argument that his competition was not great.
Same goes for Sobers, but he is not the topic of discussion here. Nevertheless, he was a champion of his time, the apex cricketer, but there were no quality A/Rs in his era. Had he played in the 80s with Imran, Botham, Hadlee, Rice and Kapil as his competition, would he still be the undisputed best of all time? Most likely no.