In answer to ccmalo,
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Lois is with Richard in the beginning of the movie. It seems that after Superman disappeared 5 years ago, she got together with him, and she truly believes that he's Jason's father (at least, until it is conclusively proven otherwise.) She's engaged to him out of some sense of responsibility to Jason, I believe, but doesn't marry him because she hasn't given up on Superman altogether (again, my interpretation.)
By the end of the movie, Lois has broken up with Richard, and Superman tells her he'll "be around," which leaves it open-ended as far as their relationship is concerned. I think the sequel will probably deal with this issue. So, in answer to your question, no, that door is not closed -- it is, in fact, opened.
As for the memory wipe at the end of Superman II, I agree with alcyonearia that it was really Clark's naivete that drove him to do it -- he really thought he was acting in her best interests. Remember that since he had got his powers back, he could no longer be with her, and he had chosen his responsibility to humanity over his love for her -- and the pain of knowing that was driving her crazy. She says as much in that final scene, which is what drives him to do the mind wipe thing in the first place.
It could even be argued that he thought he was doing her a favour, because forgetting her experience with him sort of helped her to move on; otherwise she would have been pining for him constantly. By causing her to forget, he was sparing her that pain, and at the same time condemning himself to bear the burden of that pain alone.
I'm not saying what he did was right, but that, in our dear lunkhead's two-dimensional head, he would have rationalised it that way.
-- Jude
