For me, the sweet spot for the boy's age is 13-15. Old enough to properly admire female company but still young enough for it to be taboo. Really anything under that age makes to unsavory for me. I also think the best age for the women in these pairings would be 20s and 30s. Gorgeous women in their prime who should be shacking up with grown men, but instead are letting ripe teen boys enjoy the fruits of their womanhood.

One angle I really like is that as the relationship progresses and the teen boys become more assured in their manhood, they start taking on a more dominant position with the women, who in turn start sliding into more feminine, even submissive behaviors. I think it's cute and sexy when the women start acting like girlfriends and start treating the teenage boys as a legitimate romantic partner.

One scenario I like to imagine is what if Black Cat wasn't turned off the age difference in Ultimate Spider-Man and started a fling with Peter.