Pretty hard to disagree with any of these, although I would suggest Campese is a little lucky, I clearly don't rate him quite as highly as you.
Interested whether he is considered their greatest ever rugby player in Australian rugby circles... I'd suggest Eales, Ella, Far-Jones would have a decent case wouldn't they?
If Mark Ella enjoyed a long career, he probably would have become the greatest rugby player Australia has ever produced. I know some Australian writers, David Lord for example, who would say he is Australia's best ever played. I think Ella could have become the best five-eighth ever... but he retired.
David Campese is held to different standards than most rugby players, in my opinion. For example, Campese is known for taking risks and sometimes making mistakes. But Ella did too! Mark Ella's kicking coul be foul sometimes. In his early career he couldn't kick a ball to save his life. By 1984 he was good at it. Ella also took risks, like running the ball out of his own 22 against England in 1982, getting caught by Winterbottom, turning the ball over, and letting England score a try that won them the Test. Ella was every little bit of a risk-taker as Campese, and he made stupid mistakes.
Serge Blanco is the same. He made mistakes all the time! He was frequently caught out of position and tried things that never work, but he never gets criticised for it. Honestly, Blanco and Campese are about the same in their approach to the game. Blanco was a better tackler, obviously. But Campo won Australia a World Cup.
Nick Farr-Jones... if there's one position where Australia has constantly produced excellent players - it's halfback. Most Aussies rate Catchpole their best ever halfback. One Aussie, Peter Crittle, thinks that he's the greatest Wallaby of all-time. But Catchpole isn't an immortal like Gareth Edwards is. Interestingly, Chris Laidlaw, in his book, rates Catchpole a far greater player than Edwards. John Hipwell is another... some rate him better than NFJ. But Hipwell played when Australia were a joke, and couldn't enjoy much success. So no, I don't put NFJ up there.
The best shot is John Eales, IMO, because he has no obvious flaws, has a winning record against NZ, played a long career, etc. He was voted Australia's Player of the Century in 2003, so he's a shot. Is he as legendary as Meads or du Preez?
The thing about Campo is:
Australia would not have won the 1991 World Cup without David Campese. John Eales made a famous tackle on Rob Andrew in the WC Final, and Eales put up staggering line-out figures against the Welsh - but he wasn't the star. David Campese was clearly the Player of the Tournament.