What was Frodo's temptation

[Gordis]

Originally Posted by Inziladun

If that was the case, why would Gollum, who bore the Ring much longer than Frodo and was more enamoured of evil from the start, not have been similarly affected while he possessed it?

A few reasons:
1.Gollum while sitting in his cave had no idea what Ring he had and what Powers it contained. Once he knew, he did get the ideas of Lord Gollum ruler of all.
2. The ring was still almost "dormant", much less powerful than in Mordor with Sauron in full power

And indeed you must be right, Inziladun, the smallness, meanness of Gollum's mind had to be a factor. It seems the ring couldn't simply implant Sauron's ideas/personality in any mind, it had to have something to work on, some response. Gollum was content with his cave, his fish and his Precious. Maybe, unlike Gollum, Frodo had a broad outlook on things, cared about the World, not only about himself. Sauron also "cared" about ME, in his own twisted way. Note how the ring couldn't affect Tom, who cared only about his little land and was not interested in the rest. He didn't wish to better Middle Earth, while Frodo and Sauron did.

Originally Posted by Inziladun

I had always considered that statement to Gandalf, coupled with Frodo's guilt about his ultimate failure in not casting away the Ring of his own accord, to be the explanation of his inability to enjoy the Shire afterward. Certainly the loss of the Ring left a lasting impression upon him, but it is only on the anniversary of its destruction that we see him openly mourning it.

Frodo gives the reason himself and you have cited it: "Though I may come to the Shire, it will not seem the same; for I shall not be the same" He has drastically changed himself, that's why. He is not at all the same hobbit who left the Shire a year ago, not even close. And I think the loss of the Ring is his biggest pain throughout, though he tries not to speak of it. It is like a part of his soul is ripped out.