There are five first basemen who played over 150 games last year and had an OPS over 1.000. In fact, if you count Edgar Martinez there were six. The clear top 3 are Helton, Delgado and Giambi. The next tier would include F. Thomas and J. Bagwell. Martinez is next, followed by a cluster including Will Clark (130 games), R. Palmeiro, Mike Sweeney and Jim Thome.
To distinguish between these players, you simply need to decide what you need. Giambi, Delgado and Helton are all on-base monsters, checking in at .476, .473 and .460 respectively. There were six first basemen who had over 100 walks and also struck out fewer times than they walked. Jon Olerud is the only one who hasn't been mentioned already (the others were Giambi, Delgado, Thomas, Helton and Palmeiro).
Todd Helton also just missed a slugging percentage of .700 (he finished at .698). There were five first basemen who slugged over .600, with Delgado, Giambi, Thomas and Bagwell joining Helton on the list. Brad Fulmer had a slugging percentage of .558 in 133 games. A. Galarraga (141 games) checks in at .526.
Ok, so we have covered most of the obvious everyday first basemen prospects....who is left?
Mark Grace and David Segui are both good glove men and get on base at a steady clip (.394 for Grace and .388 for Segui). Sean Casey (.517 SLG), Ryan Klesko (.516 SLG) and Derrek Lee (.507 SLG) have some pop.
Mark McGwire is going to make the draft very interesting. He had an OPS of 1.229 in 89 games, and may be eligible at 1b, 2b, ss and LF. He had 321 PA in 89 games, so with the 150 percent rule he can average 5.4 PAs per game. That shouldn't be a problem. Other attractive platoon prospects include Dave Hansen (.985 OPS in 102 games at 1b, 3b and OF but only 221 SL PAs) and John Vander Wal (.972 OPS in 134 games, can also play OF).
For fun, you might consider drafting super subs Jeff Manto (OPS of 2.657 in 7 games) or Chris Donnels (OPS of 1.125 in 27 games, can also play 2b, 3b and OF).