Jeff Bagwell put up big power numbers, but not quite as big as some of his contemporaries. He ran the bases well and played good defense, but at a position where those things are hardly considered by many fans.
The case for Bagwell as a Hall of Famer
His career batting line was .297/408/.540, giving him an OPS of .948, which ranks 21st in MLB history. Some of that is due to his having played in a great era for offense (though he also spent most of his prime playing his home games in a bad stadium for offense), but his OPS+ of 149 is still tied for 36th best ever, and his wRC+ of 149 is tied for 31st. He hit 449 home runs and 488 doubles; add in his 32 triples and you get 969 total extra-base hits, which puts him at #44 on the list. His 1,401 walks put him at #28 in that category. He had 1,529 RBI and scored 1,517 runs.
He won the 1991 NL Rookie of the Year Award and the 1994 NL MVP, and there's a good case to be made that he deserved that honor in 1999 too. He had five seasons with an OPS above 1.000, and four more when it was above .900, nine seasons in total in which he was one of the best hitters in the National League.
Whether by rate stats or career totals, Bagwell ranks as one of the 40 or so best hitters ever.
Additionally, Bagwell ranks 20th among all first basemen in defensive runs at Baseball-Reference, and 1st in base-running runs, and he missed no more than six games in 11 of his 15 seasons, and never missed more than 20 games until his final year.
His 79.6 WAR ranks 7th among first basemen, and ranks 2nd among first basemen who played after World War II (behind only Albert Pujols).
The case against Bagwell as a Hall of Famer
Bagwell was only 37 years old when he played his final game, and so some of his career total are not quite as impressive as many Hall of Famers'. His 2,314 hits don't look like anything special, and his 449 home runs fall short of the 500-HR standard which was long viewed as the ticket to Cooperstown for power hitters. Only once did he lead the league in RBI, only once in slugging percentage, and never in home runs. He played during a great time for offense, when many other first baseman were putting up big numbers too.
My two cents
I think Bagwell is one of the most underrated players in recent history. He had a career OPS+ of 149 and played great defense, and he was one of the few at his position to add real value on the base paths. That's the CliffsNotes version of what should be a slam dunk first-ballot Hall of Famer, and even as crowded as this year's ballot is, if I choose only five players from it to join Cooperstown, Bagwell would be one of them.
I suspect he's been punished by voters who suspect him of PED use, despite his never having failed a test or appeared on any of the big lists of names that have been published. Absent any evidence of that nature, such suspicions are equivalent to a witch hunt, one which does more t taint the game than the witchcraft itself, so far as I'm concerned. I disagree with those who vote to keep players like Barry Bonds out of the Hall of Fame, but at least there's strong evidence of the "crime" they're holding against him. With Bagwell, there's nothing but innuendo. He belongs in the Hall of Fame.