Well, like the title says... I am tempting my first real novel. I showed a few chapters to an editor and she seemed to be immediately repulsed by the main characters who are cheaters. Here's what she said: "Hana has no urgency or motivation at the moment, and no likability in the reader's eyes. You'll need to do some pretty extensive reworking to make her into someone that your reader is going to want to follow for an entire book. And Mike is not that much higher on the likability scale, either. He's having an affair with Hana... Again, he'll need to be reworked in order to be made into someone the reader wants to succeed." How would you feel? Would you follow the protagonists who are cheaters or would you more prefer the traditional love-the-wife/husband-love-the-kids-all-good-no-bad type of heroes and heroines?
If there were one word I could erase from the literary world, it would be the word likable. Laziest word in the book. I'm reading a book right now where the two MC's are absolutely despicable. In real life, I would leave the room if I knew they were there because the two are actually complete assholes. And... they are compelling as all get-out because they are interesting assholes, not because either is "likable" in any way. Yes, if your MC's are interesting people who happen to be cheating in the story and you tell me an interesting story about them, yes, of course I would follow the read through. I'm not a mind-reader, and I don't know your editor, obviously, but is there a chance you have simply hit a personal nerve with her?
Truthfully, a story without a "positive" main character protagonists will be much less likely to become even half as "successful" as a story with an antagonistic main character. Films/movies won't even take their chances with it. Even when there are movies that are supposed to be about super villains, they turn them into anti-heros... but hey, nothings impossible. I say, as long as you make them interesting I don't care. Personally, I'm all about unconventional story telling though. I'm disappointed if the main character doesn't die a lot of times and I think it's really cool when a writer can get people to connect and feel empathy for the character that does the unspeakably horrific when not given enough context, or even if it's just an observation of their decent into madness or something. In the end, there's no real "right" or "wrong" way outside of grammar, punctuation and spelling type stuff. With that said though, none of us here really have much of an idea of what's going on with your characters. Maybe it involves "the under-appreciated kid desperate for attention and resorting to getting into trouble", maybe it's just a kid with absolutely no reason other than the unconscious self-insert, or maybe they are just uninteresting spoiled little shits, I don't know. What I do know is an immoral character isn't necessarily a bad character. An underdeveloped character without developmental progress on the other hand, is a bad character.
You seem to be assuming that the issue is entirely about the cheating. That's not necessarily how I'm reading the comment.
I'm with @ChickenFreak - it's entirely possible to write deep, interesting characters with "urgency or motivation" and still have them have an affair. I'd widen your lens on this comment and see what else you could do with the characters.
Repulsive characters can be incredibly interesting. Cheating happens- personally I find it unpleasant- but I do not need to like it to enjoy reading the character. Seems there is a fault with how compelling your characters are.