Announcer: Mrs Czarnicki, what do you think of Bouncy Bubble Beverage?
Mrs Czarnicki: [As if reading off a teleprompter] It tastes like the death of my childhood hopes and dreams served to me in a twelve-ounce can.
and blindly love the second product in an equally weird way:
Announcer: What do you think of Manfred's Gamma Radiation Green Apple Fizz.
Mrs Czarnicki: [still as reading off a teleprompter] Sheer bliss! It's as if the Gods created this soda to overload the pleasure center of my brain!
The reason that I mention this odd creation of four members of Homo Indignantsmartass is that Elly seems to be an anti-matter version of Mrs Czarnicki because she seems to blindly love her children in the order that they appeared. Mike might not realize it given how often she lectures him and how she seems to be trying to run away from him all the time but Elly clearly does seem to worship the ground he walks on. After all, she let him have her house with no real questions asked and since she's all about things, that's pretty much a declaration of who her favorite is.
This makes life a lot harder for Liz. Try as she might to keep the Son from shining in her eyes, she'll never really be able to catch up to Michael, no matter how much she wrecks her life in the attempt. What that tells me is that if Mike had bought the Tiny Train House and John and Elly moved into a Martian-unfriendly condo, any attempt Liz and Anthony might make to claim the Pattermanse would be resisted.
Third in the pecking order is, of course, the 'child' who can't ruin Elly's life by talking back or standing up for himself: Farley. As annoying as it is for her to deal with what she sees as his trying to trick her into thinking that he's a mindless animal, she clearly did love him like one of her children: she just didn't love him as much as the first two because he arrived later and thus can't be as important.
Last and least is, of course, the awful, selfish and ungrateful Martian who destroyed her life, kept her from the greatness that all also-rans think that is theirs by right of a fairness that isn't fair to those who actually put in the effort to do things and also makes her feel guilty about wanting to waste time on the things she wastes time on anyway. I can't see that there's anything that April can possibly do that would remotely come close to pleasing Elly.
Why this might be seems to have a simple explanation: Elly isn't a very smart woman and can't wrap her head around the fact that love isn't a finite thing. Since she's the creation of a woman who's convinced that if someone shows affection to someone who isn't her, that third party is stealing the affection that first person has away from her, she can't conceive of a mother who can love her children equally. Love, you see, has to be rationed.