When I was 22 I met a 30 year old woman that simply was amazing. We got along great, and as much as I wanted to date her, she said it wouldn't work out because supposedly I hadn't experience enough women to see what I really wanted. Now, I don't know if that was her excuse to get rid of me, but looking back at the situation, she was somewhat right. So with that I mind, I would say that it really depends on the guy and his life experience. If he really thinks that he is ready for marriage with an older woman, then it shouldn't be a problem. However, I would be hesitant to say that most guys in their early 20's know what they really want, but that is not to say that there are some out there that are very mature for their young age.
I think it depends on when this age gap is occurring. If you are 20 and he is 4 years younger, then I think it is a much bigger deal than if you are 30 and he is 4 (or 8) years younger than you. It really depends on what sort of life circumstances you two are going through and how mature he is. I think it is possible for everything to work out well between you if you are compatible personalities and if you are both comfortable with the age difference. Personally, I think age is rather unimportant since it's not like you can choose when you were born. :)
Maybe not 3 or 4 younger since guys are always already a little less mature than girls but definitely not 8 years. That's too long because the girl already has acquired so much growth, strength, and wisdom than the guy in question.
I'm 28 and I dated a guy who is younger than me 4 years . Now after 6 months of relationship I feel like I can never live without him any more . I feel he also has the same feeling . We don't have any probs . The only prob is what other people around us will think about this . As am a very sensitive girl and I can never tolerate negative comments from others . I wish this joy lasts for ever :)