This is actually a sad quality in LeChuck's character in my opinion. He only believes that he loves Elaine, when deep down inside, the guy has no clue what it means to be in love. You saw what LeChuck has done to Elaine and what he is willing to do to her. He has abducted her, abused her, tortured and murdered her friends and family, and even attempted to kill her and reanimate her. Anyone in their right mind would not do those things to someone they were truly in love with.
LeChuck does not truly love Elaine, but only thinks he does because of his own sick and twisted definition of the word: to cook, clean, and have sex with. He most likely was never taught what love was and Elaine may have been the first person to even be a little nice to LeChuck until she learned of his true nature, so he thought she would be perfect for him. In my opinion though, I don't think LeChuck knows how to love. I mean he has done things to Elaine that he has done to his worst enemies. I think Tales established what LeChuck has always wanted from Elaine, to be his servent. That's my take on it.