Motherhood Is Superior

A Double Standard inherent in several works state that mothers love their children more than their fathers do. Presumably the idea comes from the fact that since it's women who carry children, they are somehow more "connected" to them. This is especially present in works where the single mother is so much more common than single fathers, and when they "come back" (for one episode because Status Quo Is God). they're usually unloving or unreliable deadbeats.

Examples of Motherhood Is Superior include:

Anime and Manga

Rurouni Kenshin: In the epilogue, Kenshin and Kaoru have a child who is a boy named Kenji. A block of text clearly states "Loves his mother" complete with Kenji eager to hold onto Kaoru. Another block of text clearly states "Hates his father" complete with Kenji eager to pull Kenshin's hair when he tries to hold him. The kid is only a few years old, and it's not like the father has done him wrong or anything!

Film

This is apparently the entire point of the movie The Forgotten: Julianne Moore plays a mother still grieving over the loss of her son in a plane crash some time previously and suddenly wakes up to find that no one even remembers he existed, not even her own husband. She talks to the father of another child who died in the crash and he doesn't remember he either and only when shown physical evidence of her does he finally remember only to be taken away by the mysterious force stalking them. At the end this is all revealed to be part of an alien experiment to test the "mother-son bond", and whether it could be destroyed. Apparently not, since despite the aliens' best efforts, her memories cannot be erased. Eventually the kids are brought back and the dads don't remember a single thing. Unfortunate Implications all around.
In A.I.: Artificial Intelligence, the father brings a robot son home hoping to "replace" their comatose real one, mostly as a means to distract his wife from the grief. When the wife manages to bond with the son, he becomes increasingly jealous and hostile.

Literature

Turns up in a lot of Jodi Picoult books. In Handle with Care:

Charlotte: Oh, Sean...You're the best father. But you're not a mother.

In CS Lewis's The Great Divorce, one of the damned souls thinks this is true. Her brother in Heaven gently informs her that her father and daughter revolted over her mourning for her dead son not because they were less loving but because she was obsessed and uncaring. At one point, one character points out to the narrator that she would gladly demand to take her son to Hell to keep possession of him.
In Death series: Subverted with Eve Dallas, because while her father Richard Troy was a Complete Monster and child molester, her mother, who has many names, is fully revealed to be a Complete Monster as well in New York To Dallas. At least her surrogate mother Dr. Mira and her surrogate father Ryan Feeney treat her much better! Initially subverted with Roarke, with Meg Roarke and Patrick Roarke being both Abusive Parents and Complete Monsters, but then played straight when he finds out in Portrait In Death that his birth mother was Siobahn Brody, who loved him and didn't see what a monster Patrick Roarke was until it was too late!

Live Action TV

A sort of inversion happened in an episode of Criminal Minds: the mother throws all the standard accusations at the father claiming that since he stopped doing things like celebrating their dead child's birthday, he didn't care about him. However, said woman is also going on a psychotic rampage caused by her grief while the father's subdued reaction is portrayed as more appropriate.

Video Games

Subverted by Final Fantasy VIII: Raine is Ellone's mother figure, but her bond with Laguna (Raine's main squeeze, basically.) is much weaker. However, after she gets kidnapped by the Estharians, Laguna goes Always Save The Girl, daughter-style.´

Newspaper Comics

Close to Home: One episode has a mother, father, and child. The child is put on a measuring device that determines if he loves his mother or his father more. The machine has its pointer on the mother's side. The mother and child are holding each other happily, while the father stands there looking unhappy.
Pearls Before Swine: Possibly deconstructed in one episode where Pig is talking to Goat about his neighbour. His neighbour had married this one woman, and everything was great...until the wife had two kids. Then the wife and the kids, who love each other, started treating him like a non-entity. The neighbour has come to the conclusion that she was only using him to get some kids. Goat tries to point out that there is more than one side of a story, and Pig agrees. Then the last panel shows the neighbour was right. The kids and wife are sitting on him, he gets milkshake on his head, and one of the kids says "I spilled milkshake on the couch again, Mommy." She simply says, "That's okay. I was thinking of trading this one in, anyway."