And now to talk about Mario and Peach's relationship.
Mario is in love with Peach. BUT that happened AFTER he saved her the first time. And his being in love with her is not the reason he goes to save her, he is just a good guy like that. That being said, Mario believes peach deserves the best, he wants her to be happy, even more than he would be with being with her. When he gets to be around her, he is happy and is glad to be in her presence. She is kind, caring, she is a great baker and chef, she is also interested in what he's been doing. Mario and Peach could converse for hours. Mario is not a knight of the kingdom, but people often believe he is. Mario also allows himself to vulnerable around Peach, because deep down, he knows she would never judge him. I do believe Mario does think he is not good enough to be with Peach, which is why he doesnt make a direct move.
Peach is in love with Mario. No ifs ands or butts. Peach finds Mario down to earth, kind, attentive, and honest. Peach finds that people often sugar coat things around her, she feels people are never honest with her, She never has that problem with Mario. Mario treats everyone with dignity and respect. Mario believes Peach has her own autonomy. Peach believes Mario is someone that can do anything regardless of the impossibility. He has a determination that cant be broken and he has found ways to save the day regardless of the foes. Peach firmly believes Mario is a True hero. Peach also loves Mario's mustache, often complimenting it. Peach has had many suitors in the past try and woo her, but she has turned them all down, bowser especially. Because Peach has her eye on one man, and he is super. She just wishes one day he will view himself the way she sees him. Until then, she will wait as she watches him eat the cake she made with a smile on her face.
There's a comic by @klunsgod where Peach explains to Perry the parasol that when Mario entered her life he inadventently got her out of a spiral into depression caused by her restrictive life as princess, because of his grounded and unconditional kindness and the excitement his adventures brought to her life. This comic has been downloaded into my brain, and is now a headcanon I have.
I also remember Peach's dialogue in Mario & Luigi: Paper Jam, where she talks about how much pressure she's under to maintain her image as a princess to everyone, and says that she often thinks about things like dying her hair purple, or shaving it all off, but has to push those desires down to avoid destroying her image. This lead me to a headcanon where Peach is an inherently a gentle and unassuming person, but is also a preassure cooker of stress, self conciousness and repression, and Mario is the first person who made her feel comfortable enough to unwind in years.
This headcanon is a bit dark, but I feel it's grounded enough in facts about Peach's life from the games that it works for me. She was raised as a princess in the palace since birth. She doesn't seem to have any parents, probably delivered straight to the castle by the stork. The best parent she had while growing up is probably toadsworth. She mentions being given strict instructions to behave like a delicate princess by her ministers, which she doesn't seem very happy about, but obeys anyway.
