I agree with Hopeful 55. Been divorced for years and have dated men from 20 years younger to 5 years older. It depends upon the individuals. The age difference never mattered to me. It really depends upon that "special attraction" and if you have enough like interests to keep it going. If you fall in love, it's great.
My last partner was 20 years younger than I. We were together for 20 years. It was the most wonderful 20 years of my life, but I was realistic. Eventually, he would want children, and when he started mentioning that issue, it was over for me. I set him free and we are best friends today.
There is an acceptable and realistic age gap for a successful relationship. I read recently,that people closer in age have a greater chance of success. Personally, I have always been attracted to older women and have had three relationships with older women ranging from 8 to 13 years in Difference. In two of them,we simply wanted different things out of life. In the third and longest relationship we were simply at different stages of our life, I was 22 she was 35. So, my take on the age game is that its complicated and there is no difinative answer to the question.
Age is just a number, but I would feel strange dating a man my adult kids's age or gasp, my adult grandson's age. It's been my experience, having been hit on by dozens of younger men, they are only looking for a fantasy with a sexy older woman, not a love relationship.
As long as the male is over 21, my guess would be whichever age gap is comfortable for both parties. I once had a crush on an celebrity who was 20 years my junior but it was safe.....he never knew! Realistically, for me, I would be comfortable with a male no younger than 10 years my junior....as he would have experienced much of what life has to offer him.