I don't care or worry about it. To me mere "attraction" doesn't automatically mean "take action." Crushes from afar are just for fun. I'm married, but I still like admiring men, women, any age, any ethnicity. Enjoying other people and human beauty doesn't mean I'm going to do anything about it. DH and I sometimes do it together even. We did it even when we were dating. He's long grown used to me crushing on whoever periodically and it fading and being replaced by some other crush.
For actual dating, when I was young I preferred my own age or a year or so up or down. In High School or early college that seemed more manageable to me to date people in my own grade or one up or down. I didn't want too large a maturity or experience gap when I was still learning the dating ropes.
I'm married now but if I were back in the dating pool for some reason I'd be more open to a larger age gap. Maybe 5 years younger and up to 10 years up.
But probably 15 years gap at the most. I just couldn't bear 20. That starts to get too close to old enough to be my own parent or my own kid. I'd also worry about too big a gap in age translating to too big a gap in interests. But who knows. If I were 80, I might very well have to open the "crushing" age gap wider since there's not a lot of 100 yr olds but there's many more 50 & 60's! LOL.
A.