Agreed on all counts. He may have been great, but could have been far greater. He never worked on his game in the off season, or even tried to stay in halfway decent shape. He also postponed surgery that he should have had done at the beginning of summer until summer was over and training camp starting - just so he could have the summer off. He never took the regular season seriously. Constantly starting the regular season overweight, or recovering from surgery cost him lots of games, and led to further nagging injuries that cost him even more games. If he would have done nothing else above and beyond staying in reasonable shape suring the off season, he would have had a much greater career and would have had offensive stats comparable to Karl Malone or maybe even Kareem.
He also never worked on improving his game. He simply relied on his unique combination of size and stength (and quickness, early in his career before he got fat) to overpower his opponents. He seemed to really admire and respect Hakeem, but never put in the effort to learn low post moves comparable to Hakeem or the other great centers. Imagine a player of Shaq's size and strength and the low post moves of Kevin McHale, or even just a halfway decent drop step and up and under.
And then there is defense and rebounding. Souldn't "the most dominant player of his generation" lead the league in rebounding and blocked shots year after year (or at least occasionally) during the prime of his career? Again, when it came to defense and rebounding, Shaq lacked motivation and and effort. Defense and rebounding are hard work. Shaq preferred to rest on defense and save his energy for the offensive end of the court. Of course, if he would have been in good shape, he could have gone all out at both ends and been a much more complete player.
He's often compared to Wilt, due to their physical dominance, but Shaq was no Wilt. Wilt kept himeself in great shape and hated to miss a minute of any game for any reason. Shaq generally coasted through the regular season for most of his career. Wilt was a dominant rebounder and defender. He also made himself into a great passer. Exceptional size and steength and poor FT shooting is where the similarities between Shaq and Wilt end. Wilt was a much more complete player who worked much harder both on, and off the court (insert obligatory joke about 20,000 sex partners here).
In the end, Shaq will be remembered as a great, physically dominant player, but if he would have shown more dedication to conditioning and improving his game, he could have been the greatest ever. He just lacked the drive and self-motivation of players like Jordan, Bird, and even Kobe.