Originally, Clark's first love was Lana Lang. When she left for college and he went and traveled the world.....their love went away. (in fact, I believe in one of the Superman movies, Lana returns (played by Anette O'Toole who plays Martha Kent on Smallville) and they start to have feelings for each other again.

Clark seems to fall in love with Lois (in the comics and movies) gradually, even though he does think she is attractive. But they also have a very much love/hate relationship filled with sarcastic comments....especially since Lois is so full of herself and thinks she is so much better than Smallville, Kansas farm boy

Sort of a wierd "love the man" situation. Best way I see it, Lana Lang was and IS Clark Kent's first love. Lois Lane is Superman's true love. Think of it that way.

In the comics, when Superman was under the care of Lana Lang while Lois was on assignment, Lana made a pretty clear observation. Lana loves Clark Kent, the man. She also brought it to his attention that Lois loves Clark Kent but at the same time is loving SUPERMAN. That's the difference between them. Even when Lois and Clark went to Smallville to visit Ma & Pa Kent and the farm was attacked a few months ago (don't remember the issue) dinner was tense becuase there was Clark, Lois, Ma & Pa Kent, Connor (Con-El or Superboy) and Lana Lang all having Thanksgiving dinner and out if comes that Lois DOES get off knowing that she's married to Superman (Ma Kent really brought that to the table).