1. It varies from person to person. I have liked plenty of younger guys but mostly dated around my own age (within 1-2 years). 2. It changes as people age and also can change depending on what they are looking for. When I was 24 and wasn't looking for anything serious the youngest I saw was 20. If I were dating today a 20 y/o would look like a kid to me. A 23 y/o might be hot but probably wouldn't be someone I'd be interested because they're most likely in a different life stage than me. 3. Combo of 1 & 2. Different men will look their "best" at different ages and different people may think that man's "best" is at different ages.
I find 30 + actors attractive, but I haven't actually had the opportunity to date any that much older than me, but I think I would if they're really hot. lol I wouldn't mind even 2 years younger than me to maybe 8 years older on average.
At this point in my life, and based on my experiences, I prefer to date older. However, if I find someone that I click with and is a bit younger than me, then I would give us the opportunity to see where it goes.