I think Maggie was more annoying than Holmes tbh! Though, the ending scene of Rachel and Bruce in BB is probably the worst moment of Rachel if you ask me! That weird smile of Katie...uuuurgh!!
I really liked Pepper Potts in Iron Man as well! That relationship was really well done and interesting!
I also like Liv Tyler in The Incredible Hulk! But that's maybe because I really really like Liv Tyler herself.
I'm not sure if Mystique counts as a love interest, but I really liked her in X-Men: First Class.
I have a feeling though that Emma Stone/Gwen will be the most likeable love interest/main female character in the recent wave of superhero movies!