There are so few players who compare to Pujols from the start of a career that I thought we could modify our criteria just a bit and 1) look for players who had nine consecutive seasons as good as Pujols's at any point in their careers and 2) not insist that those nine seasons be as good as Albert's weakest season, just somewhere near that standard.
Even applying that looser standard, I find only 19 players in history who have had comparable strings of nine consecutive years. All 19 of those players are Hall of Famers with the exceptions of Barry Bonds, Pete Rose and Manny Ramirez.
[Hank] Aaron is the gold standard when it comes to consistency. Pujols, though, is gaining. And that seems to be what drives him: to be great every year. He has never batted lower than .314. Never hit fewer than 32 homers. Never driven in fewer than 103 runs. His career low on-base percentage is .394--that's his low--and to give you an idea about that, Cal Ripken Jr., Ryne Sandberg, Ernie Banks, Lou Brock and Jim Rice never once had an on-base percentage that high.