I agree with .Amber. I think it really depends on the maturity level of each individual involved. I dated an older guy, I was 22 and he was 38. So a 16 year age gap between us. You would think that he would have left me for my "immaturity" compared to his, but I actually left him for that very reason. I wanted to settle down, raise a family, get married, have more children, etc.. and he wanted none of that, he wanted to drink, party, etc.
I'm 23 turning 24 in August, and my Hubby is 28 turning 29 this month. There's a 5 year age difference, and sometimes I still wish he was a bit more mature! lol