IMHO he's up there with the very best and is probably the best. But you can't use the massive trophy count to put him head and shoulders above the others. Footy was very different in times past. Three things changed it and made it easier for richer clubs to stay at the top for long periods.
Until the maximum wage was lifted in 1961, no player in England could earn more than £20 a week. If you were getting £20 a week at, say, Ipswich in 1960, why move to a bigger club where you might not get a regular game and you'd be on the same money ? Unless the club wanted to sell, local heros tended to stay put in those days. A young Aaron Ramsey or Theo Walcott might have spent their whole careers with one club. Carlos Tevez is unhappy enough as it is about sitting on the United bench - despite all that cash. A 1960 equivalent would never have swapped a guaranteed first team place to be one of a squad for the same pay - and after all, you can only have so many forwards in a team.
That's not to say that transfer fees didn't make a difference - but the club had to want to sell. Lots of transfers today are basically forced sales.
Another difference was retention of registration. Until the 1995 Bosman ruling the club had your registration even if you were out of contract. To sign you, another club had to stump up. Turnover of players is much higher since Bosman - before, a player who wanted to leave might kick his heels when his contract ended, if his club got stroppy. These days he'd be a free agent - so transfers tend to happen when the player's still got a couple of years left on the contract.
Last, the footy TV cash and the marketing cash. Sky wasn't around in those days - the clubs earned what came in at the gate on matchdays unless they had a wealthy sponsor, and the mega-rich of those days didn't watch a lot of footy.
So a great manager way back when could (with the right club) disband an ageing team of stars and wield the chequebook, but not to anywhere near the same effect as today. Rebuilding was a slower process (and I'm aware that Ferguson has a fine record in bringing on new talent at United).
Mind, Herbert Chapman sounds a bit of a cunning old fox himself. What would El Tel, 'arry and Cloughie make of his teetotal transfer dealings ?
We arrived at the hotel half-an-hour early. Chapman immediately went into the lounge bar. He called the waiter, placed two pound notes in his hand and said: "George, this is Mr Wall, my assistant. He will drink whisky and dry ginger. I will drink gin and tonic. We shall be joined by guests. They will drink whatever they like. See that our guests are given double of everything, but Mr Wall's whisky and dry ginger will contain no whisky, and my gin and tonic will contain no gin."
The inebriated guests were then beaten down on the transfer price !
UPDATE - James Hamilton has more (and better-written, and better-researched) - on Herbert Chapman.
PS - three home wins in a row ! The Baggies may be bottom, but there are only six points between bottom and ninth ! Surely United and Chelsea will be nervously glancing over their shoulders ...