in fact, if you want to find out who the best century maker is, you would want to get all the centuries divided by the number number of frames of his entire career.  i dare say that hendry wouldnt be top, he's been pro since 1986. ronnie MIGHT be up there, because he turned pro in 1992
if anything it might be judd trump, hes got over 100 only 5 seasons. 
 
		 
Trump tried for a 147 against Higgins, broke down, lost the frame. 
Had he simply tried to win and succeeded, he would have had one more game, Higgins would have had one less. 
Might have made a huge change in the game.
So 147s, while interesting, are only one frame.
Same with centuries
At one time a 147 in the World Championship was worth 147,000 pounds, plus 20,000 pounds for highest break. Making a 147 was worth far more than a second place finish.
That sort of payout has gone the way of the dodo.
When you compare Hendry and O'Sullivan, it is quite simple. 
What baseball style statistics might suggest is not relevant.
 Hendry
Ranking Tournaments - 36
Hendry
Ranking Tournaments - 36
World Championship 	1990, 1992-6, 1999
UK Championship 	1989, 1990, 1994-6
Grand Prix 	1987, 1990-1, 1995
British Open 	1988, 1991, 1999, 2003
Asian Open 	1989, 1990
Dubai Duty Free Classic 	1989, 1990, 1993
Regal Welsh Open 	1992, 1997, 2003
International Open 	1993, 1997
Regal Scottish Open 	1999
European Open 	1994, 1995, 2001
Thailand Masters 	1998
Malta Cup 	2005
Non-ranking - 32
Scottish Professional Championship 	1986-8
Winfield Masters 	1987
New Zealand Masters 	1988
Wembley Masters 	1989-93, 1996
Scottish Masters 	1989, 1990, 1995
Pontin’s Professional 	1990
Hong Kong Challenge 	1991
Indian Challenge 	1991
555 Challenge 	1991
European Challenge 	1991
Premier League 	1991, 1992, 1994, 1995, 2000, 2004
Irish Masters 	1992, 1997, 1999
Malta Grand Prix 	1998, 2001
Red Bull Super League 	1998
Champions Cup 	1999
O'Sullivan
Ranking - 22
World Championship 	2001, 2004, 2008
UK Championship 	1993, 1997, 2001, 2007
Grand Prix 	2004
British Open 	1994
Regal Welsh Open 	2004, 2005
German Open 	1996
Regal Scottish Open 	1998, 2000
European Open 	2003
Northern Ireland Trophy 	2008
China Open 	1996, 1999, 2000
Irish Masters 	2003, 2005
Shanghai Masters 	2009
Non-ranking - 22
Wembley Masters 	1995, 2005, 2007, 2009
Scottish Masters 	1998, 2000, 2002
Champions Cup 	2000
Riley Superstar International 	1997
Liverpool Victoria Charity Challenge 	1996
Benson & Hedges Championship 	1993
Premier League 	1997, 2001, 2002, 2005 (04/05), 2005 (05/06), 2006, 2007, 2008, 2010
Irish Masters 	2001, 2007
On this link
http://www.snookerisland.com/forum/viewtopic.php?f=25&t=1146
Hendry earned £345,494.40 per year - Total £8,637,360
O'Sullivan earned £336,445.00 per year - Total £6,056,010