It's all about your personality and what you find attractive in people of the opposite sex, or same sex if you're gay.
Some guys find older women attractive because they've come to realize what they want from a man, and don't play annoying little games. Some guys like younger women because of the games they play.
A typical woman around 20 is attracted to older men because she is looking towards the future and wants a stable man to settle down with. Many women around 30 are attracted to younger men because they make them feel pretty by choosing them over the hot young girls.
In every relationship there is a dominant partner, to at least some degree. If you're attracted to older women, you are probably more of a submissive person looking for someone to take care of you. There is absolutely nothing wrong with that, and if you can realize and accept it then you're one step closer to finding that special someone, because you know what you're looking for.
Personally I'm more of a traditional guy, and the closest thing I've had to an attraction to an older woman was with a girl 3 months older than me (but dumb as hell, and a year behind me in school) because I like being the aggressor, and my instinct is to be the chivalrous guy that swoops in and takes care of all of the woman's problems. But being a libertarian at heart, I say go with what makes you happy, and as long as you aren't hurting or taking advantage of someone then you aren't doing anything wrong.