Sauron was master. Simply put it was
HIS power he poured into it and by claiming it somebody is, in essence, able to usurp a good portion of his power.
On a side note, maybe why it kept slipping off Bilbo's hand and Gollums is because they are hobbits and have generally smaller fingers than Sauron, though then it must be assumed that Isildur had rather dainty fingers too
