It goes without saying that Sauron desires power. Why else would he try to conquer all of Middle-earth? But even if Sauron is a power-hungry maniac (and he definitely is), the interesting thing about him is that he lacks the ability to make new things on his own. There appears to be a limit on Sauron's power even at the start of the War of the Ring. Don't get us wrong. Sauron can certainly still do tons of horrifying damage with the power that he does have. But in The Two Towers, it's clear he'll never truly achieve the kind of god-like domination he seems to crave.
Tolkien's negative representation of the stone walls and hot furnaces of Isengard suggests his strong suspicion of the power of industry and its effects on the green things of the world.
When Sam finally realizes that the best part of him is his heart, it shows that he has totally given up any dream of power. You can't deeply love someone, like he does Frodo, and want to control them at the same time. That makes Sam surprisingly qualified for Ring-bearing.