The only people who don't have to fight the Ring's temptation are those who it does not bother trying to tempt, quite simply. Even Gandalf and Galadriel have moments of difficulty when Frodo offers them the Ring - and that had more to do with the Ring knowing how much havoc could be wreaked if it ensnared either of them than it had to do with Frodo's strength. By the time it came into Sam's possession it had a huge incentive to mess with anyone at all, because it was drawing close to destruction. My point isn't that Sam was alone in resisting, my point is that he was alone in making resistance look completely and utterly effortless.