Mediocre bait, but I'll bite.
1. Unlike you, Marco isn't annoyed by Star. He thinks very highly of her, considering her "the coolest girl he ever knew", and values and enjoys her company a lot. She's the person he is the most comfortable around, and they understand each other perfectly. Meanwhile, Marco still feels nervous and uneasy around Jackie, whom he still hasn't got to know well (like he said she deserves in Sleepover). And it's not like they didn't have time to get comfortable around each other - they just didn't seem to be particularly willing to, especially Marco, who spends most of his time with Star and who has repeatedly left Jackie hanging to check on Star. If Jackie is the "perfect" girl for him, he sure doesn't act like that, as his heart clearly seems to lay with someone else.
2. Yes, Marco and Star argue and fight sometimes. That's only healthy, as in the end they always talk things out. Marco and Jackie, on the other hand, have no conflict whatsoever - not because they are "perfect" together, but on the contrary, because they lack the communication and understanding that Star and Marco share. Jackie is just chill with everything Marco does, and he doesn't really know her well.
3. Marco needs Star to grow as a person. They bring out the best in each other. Star is overly energetic, yes, that's why she needs someone to keep her anchored. Meanwhile Marco is "the Safe Kid", he needs someone to push him forward. "Cute and perfect" isn't just a meme, they are literally perfect for each other. Jackie just accepts Marco for who he is and helps him accept himself, which is also good, of course - but Star inspires him to be much more than that.
4. Marrying Star comes with becoming a royalty, something that Marco has expressed interest in ("man, I'd like to be Queen!"). Marrying Jackie comes with a boring old life on Earth and... skateboarding lessons?
Hips aren't everything. Jackie can't compete. I'd write more points, but character limit.