Brown was a stalwart of the Australian eleven in the mid to late 1930s.In 1939 he was one of Wisden's Cricketer of the Year:
"...his choice for the recent  tour to England caused considerable and sometimes bitter criticism. Fortunately, the Australian selectors had sufficient vision to realise that such a batsman does not lose his powers at the age of 25, and in England Brown rose to the occasion splendidly. After an innings of 196 not out against Northamptonshire, the tour was one long succession of triumphs for him. Scoring 206 at Lord's in the Second Test, he joined the select band of those to bat throughout an innings. This fine performance, following a fighting century in the Nottingham Test, put the seal on his fame, and finishing second to Bradman both in average and aggregate, Brown ranked with his captain in consistency. Besides batting with a charming skill, coolness, thoughtfulness and certainty, Brown was magnificent as a fieldsman, and he owes his development in this direction to persistent training. Day after day he used to run with professional sprinters in order to learn anticipation and quickness off the mark. A cricketer of remarkable powers who has not yet touched his top form, Brown at present is slow to unfold a wonderful array of strokes.
I never saw Brown play, but I did see Norman O'Neill bat and field. Need I say more?
If you're not convinced read Gideon Haigh's assessment on Cricinfo :
Norm O'Neill failed to fulfil expectations of his batting only because the forecasts of his greatness were so widespread and demanding. Never "the new Bradman" he was tagged at the outset of his career, he was nonetheless a back-foot player of astonishing power, and a broad-shouldered Adonis who gave off a golden aura of good health. He shone in his first series, against England in 1958-59, demonstrated great adaptability in India and Pakistan a year later, and adorned the 1960-61 Tied Test with 181 in 401 minutes: an innings that, in Jack Fingleton's words, "sparkled like champagne". In 1961 EW Swanton was moved to write that O'Neill "reminded us that the art of batting was not dead, merely dormant". Always a nervous starter, he found form more elusive after that, but he was only 28 when Australia dispensed, rather peremptorily, with his services.
Need more? Read what Wisden said in 1962 when he was one of its five cricketers of the (preceding) year:
To be true, a high innings by O'Neill is a thing of masterful beauty. His stroking is delectable, immense in its power. But O'Neill has often got himself into a rut. He is a bad beginner. He seems to come to the middle as if he has been fretting in the dressing-room, worrying about the future. So, then, he often does something rash very early in an innings. He has had two slips from grace and only because he used his right hand too much, allowing a big gap between his hands on the handle, and then turning his right shoulder too much to the bowler.
If he can conquer himself for a start -- his rashness, his uneasiness -- O'Neill will not only have many more very big and thrilling scores (he's bound to have them) but he will have them more consistently. His rashness, too, often comes into his running between the wickets. For all that, he has given us some of the most glittering post-war innings. A glorious fieldsman, he has the dream throw.