Amazing =/= Attractive or whatever other adjectives you want to use. >_>
It can mean respect, it can even mean a tinge of fear.
Lois possibly awes him to the point that he hasn't considered a romantic aspect to their relationship because...well, amongst other things, he thinks she's above his level by whatever combination of qualities she has. Diana, on the other hand, might have super powers, but eh, so does he, and she's shown some serious vulnerabilities lately. Basically, in his interactions with Lois, he hasn't seen any real chinks in her emotional armour, but he's definitely seen well enough that Diana, for all her powers and her big heart, is far from perfect.