I have to say, I absolutely LOVE this relationship! I am so surprised that more people do not see it so. And I must say I definitely do not think that Logan and Jean have only lust and not love for each other.
Here's what I think: Jean is totally in love with this great guy named Scott. He asks her to marry him, and she happily says yes. But then this dark, dangerous, mysterious guy named Logan shows up and mocks her fiance and teases her and somehow manages to sweep Jean off her feet. He makes her feel things she's never felt before -- it's almost as if she never really knew what being in love was until this. But, alas -- it's too late! Jean is already committed, already engaged to Scott the Wonderful, and she is too honorable and too afraid and too proud to break it off, especially for this roguish wanderer. But inside, much to her own dismay, she's deeply drawn to him. They are both very passionate people, though Jean is in the habit of repressing this passion, whereas Logan makes no effort to hide his feelings (and Kudos! to Logan for having the guts to risk Jean's rejection by making his intentions so plain).
So I like it, because it sets up a great dynamic. It's more than just a love triangle plot device or a simple lust thing, because real love and real loss are involved. And I haven't even begun to speak of Logan's feelings for Jean -- he undoubtedly loves her, very deeply. And if he loves her partly because she reminds him of a long-lost love, so much the better -- I think that's touching. It shows more of tough Logan's tender side.