Top All-Time First Baseman: Lou Gehrig #1; Jimmie Foxx #2; Pujols #3
Pujols has a ways to go to exceed the great Lou Gehrig as the top 1st Baseman ever. Gehrig has a higher BA and OBA; slugging % about even; and of course is way ahead of Pujols in totals for all the offensive categories.
If Pujols has 5 more years at this level, then we can talk about whether Pujols or Gehrig is the best. Right now, I'd rate Pujols a close 3rd behind Jimmie Foxx.