You want some examples here they are.
Hobbs played in 3 different countries (England, South Africa and Australia), never went to the sub continent, probably never faced a bowler like Murali, Kumble on spinning wickets.
Hayden played all over the world, faced different bowlers on all kinds of different pitches. Despite your belief not every wicket is flat these days. He has one of the best conversion rates by a opener, he did well in India as well as at home. Were the Aussie pitches really the flattest in the world?
One other thing. Can you find for me the bowlers that Hobbs faced? No doubt its hard facing bowlers on uncovered pitches but really who were they?
At last, some bloody discussion.
Not every pitch that Hayden played on was flat, but it's no co-incidence that Hayden never made substantial, chanceless runs on a pitch that offered something for seam bowling, against good seam bowlers. I've never doubted Hayden's talents against spin bowling either, that's the 1 thing he's got going for him.
As for the bowlers Hobbs played against;
Against South Africa he scored big runs against a highly regarded leg-break bowler Aubrey Faulkner; Jimmy Blanckenberg who was a medium pacer with unerring accuracy and movement and was said to have been a real handful on the matted wickets of SA; Bert Vogler who in his time was seen as the best bowler in the world and bowled a variety of medium pace and legbreaks. He apparently could deliver the off-break with a leg-break action, and was incredibly difficult to pick.
Against Australia he scored big runs against Tibby Cotter who was supposedly incredibly fast. He was short but generated extreme pace from a strong chest and shoulders. It's said he actually broke stumps or bails on at least 20 occasions due to his extreme pace; Ranji Hordern a bowler that's been compared to Ajantha Mendis and was said to have mastered the googly like no other Australian (including the likes of Clarrie Grimmet and Bill O'Reilly); Jack Gregory a bowler that's been compared to the West Indian Wes Hall. He was a giant of a man that bowled incredibly fast, and was very unpredictable. But he's regarded as a fine, fine bowler;
The more well renowned Australian's include Arthur Mailey, a leg-spin bowler that was said to have turned the ball a mile and had incredible detirmination and would never give up his search for wickets; Clarrie Grimmett, a fine leg-break bowler, one of the best of all-time. He bowled with incredible accuracy, had a wealth of variation and a fine temperament.
Then from the West Indies Hobbs would have faced Herman Griffith, a very accurate, patient and talented seam bowler from Barbados; and Learie Constantine, who bowled with a bounding run, a high, smooth action and considerable pace. He was a fine cricketer.
Then not forgetting the guys Hobbs would have faced in Domestic cricket, where he made an unprecedented 199 FC centuries. He'd have faced guys like Harold Larwood, Sydney Barnes, Maurice Tate, Headley Verity, Bill Voce and Wilfred Rhodes. Hobbs faced some mighty fine bowling, in an era of uncovered wickets, many of which would have been wet wickets. He was also regarded as a better player on wet wickets than Sir Don Bradman.
From Cricinfo:
"An astonishing statistical fact about The Master is that of the 130 centuries to his name in County cricket, 85 were scored after the war of 1914-1918; that is, after he had entered middle-age. The more his years increased the riper his harvests. From 1919 to 1928 his seasons' yields were as follows:
1919 2,594 runs average 60.32
1920 2,827 runs average 58.89
1921 312 runs average 78.00
(a season of illness)
1922 2,552 runs average 62.24
1923 2,087 runs average 37.94
1924 2,094 runs average 58.16
1925 3,024 runs average 70.32
1926 2,949 runs average 77.60
1927 1,641 runs average 52.93
1928 2,542 runs average 82.00
I never saw him make a bad or a hasty stroke. Sometimes, of course, he made the wrong good stroke, technically right but applied to the wrong ball. An error of judgment, not of technique. He extended the scope of batsmanship, added to the store of cricket that will be cherished, played the game with modesty, for all his mastery and produce, and so won fame and affection, here and at the other side of the world."
Hobbs' batting partner for a lot of his Test career, Herbert Sutcliffe had this to say about him: "I was his partner on many occasions on extremely bad wickets, and I can say this without any doubt whatever that he was the most brilliant exponent of all time, and quite the best batsman of my generation on all types of wickets. On good wickets I do believe that pride of place should be given to Sir Don Bradman. I had a long and happy association with Sir Jack and can testify to his fine character."
You talk about Hayden scoring runs at a good average in 100 Test matches, Hobbs averaged 50.70 in 834 FC matches, in an era of some magnificent bowlers, uncovered pitches and no helmets. He's one of the greatest batsmen of all-time, let alone openers. He stands above them all as far as opening the batting goes, with only Herbert Sutcliffe, Barry Richards and possibly Sunil Gavaskar coming anywhere close in my eyes. Brilliant, brilliant cricketer, and a magnificent opening batsman.