What makes Superman Returns great to me is Brandon's Superman and the special effects. I found KB not only to be horribly miscast as Lois (she looks all of 16 years old!), I just don't like the choices she's made IRT Richard. I've discussed this with other people and the only explanations for her actions I can see are the following:
1) The mindwipe kiss at the end of SII made her forget
everything and when Supes left she felt rejected and got involved with Richard. Since she didn't remember her relationship with Superman, I can see how she would be able to move on that quickly. Then, when she found herself pregnant, she assumed it was Richard's and so did Richard. In that case, though, I find the ending very dissatisfying. In my mind, Lois would never let Superman just fly off like that without confronting him about Jason.
2) She knew Jason was Superman's and she let Richard believe he was his. In which case I would find her behavior despicable and in my eyes there would be no excuse for it. Talk about destroying a character.
3) Richard knows Jason is not his son, but he does not know that Superman is Jason's father. In which case Lois must've told him she doesn't know who the father is. Either she lied, or maybe she really didn't know, given the mindwipe kiss. However, see option 1 for why the ending doesn't work for me, then.
Maybe there's another explanation I haven't thought of, so please feel free to enlighten me. But all the ones listed just aren't satisfying to me, because either Lois is a liar who's using Richard, or she's just really passive after finding out Jason is Superman's son, which is so far OOC for her that no fanwank could make me accept it. I would expect her to confront him and slap him. Hard. Not let him get away with that "I'm always around" crap.
So, to make a long post short, I like SR because of Brandon's Superman and the FX, certainly not because of Lois. And I love L&C because of Lois
and Clark and how they work so well together. Now, if we had gotten LACTNAOS in combination with SR's effects I could have died a happy FoLC

.