If they are both adults it's not inherently wrong, but I tend to be a little taken aback when I see a couple where the girl is in her young twenties and the man is older than my father. It's hard not to notice. The older you both get, though, the less age matters. I don't see a lot of couples where the man is significantly younger, to be honest, I can't think of any, other than on tv. It's more accepted when the girl is younger because historically, men are the breadwinners, support the family, etc. Its also more accepted when the girl is younger because she has a smaller window of opportunity to reproduce.
I can't see myself submitting to a man who is younger than me or even my same age...I am naturally a leader in a lot of situations, and I want someone who can lead and challenge me, has their act together, who can be serious and socially appropriate when its necessary (and completely goofy when its not necessary)...I want a strong, manly man (haha), not someone who makes me feel like I have to make all the decisions. Anyone close to my father's age or older, I draw the line..too strange for me, but some ladies are into it.
Many inter-generational relationships work out well, but people will always be curious when there's a real visible age gap. Its not my place to call someone out on a huge age difference, and its not very tactful...if God is the center of the relationship, then everything else doesn't matter.