I'd be curious about what criteria you used to come to your result.
For me older women, milfs and/or badass girls (aka fiona) are always better then the younger ones but that's just my preference obviously and the reason why i rate Amy so high is because that's the kind of women i would actually try to date in real life (career driven, sophisticated, dark past, hot, older, curvy, it hits all my checkboxes).
I actually didn't like cat all that much early on because of the hardcore jealousy issues but she got better and while i usually don't like the younger ones, you really can't have liz without her and while she didn't make it to the same tier as grandma, liz and them she's still a good character just not one of my favorites.