[Gollum the Great]

Well, I wouldn't say that LOTR Sauron was personality-less. I see him more as an evil mastermind/lord/Satan bereaved of his superweapon to conquer the world in one swift blow. After failing to locate and reclaim his weapon he simply does the smart thing: maneuver what other forces he has into position so that no one else can rival him with his ring.
One might take Gandalf's argument and state that if he'd want to keep the ring from being destroyed he should have defended Mordor with all his armies and made sure no one could get in, but look at it from both Sauron's and the unbiased observer's eye: which was more likely, that the ring would be found by an easily corrupted person, or an unique person who could resist it? And had the ring not been found, there was no point in allowing the Free Peoples to prosper and grow.
All in all though, Gorthaur in the Silmarillion was a more interesting character. There he was not totally in charge of evil, but a servant, and a powerful one at that. I believe Tolkien did not fully think out the Sauron character in LOTR, but decided to give us some history of him and show some abilities and might of his in the Sil.

Good question, Nog.