I agree with Elementary to a certain degree. I think todays game involves different sorts of players big, strong, can run 100 metres under 11 etc. Sure if the teams of the 70's and 80's would undergo the same training ands weights program they would be just as competitive, even adapt great to the 10 metre rule. However, like the run arounds and sweeping backline movements etc their game wouldn't be suited to ours. Different cultures of players, a different pedigree of player is now required to play the game.
Just look back to the 80's, you think a player like a David Hatch or Mick Neil, Paul Taylor, Mick Delroy etc with all due respect to these players who were good in their own rights would be able to compete in todays game?, i doubt that very much. Eric Grothe snr is a different example altogether though, It's obvious that Jr has inherited his genetics, and that fend of his and his speed, they were parts of Eric Grothe snr that made him great. Snr is better then Jr...why? not only could Snr run 100 metres to score a try, he could also run 100 metres to stop one. He also posssed better attention to detail in remote parts of the field, Jr doesn't display these straits.
I will say this though, if Bradman played today his batting average wouldn't be 99.4, it would be around the 60-65v mark, sorry to offend, but his average was mainly due to the influence he had over the poms. Cricket is alot more diverse these days, whitch involve different environmental aspects of locality, cricketers are alot more skilled ( eg Warne, Murali with spin bowling) and a hell lot quicker in the way the game is played!!!!. bradmans average was thanks to the dominance he had over the poms, like Warnes and Steve Waughs dominance over them, except they do that to a variety of countries!