Really it doesn't matter as long as their happy and some people don't judge their lover by looks. Sometime people would had a crush on someone older b/c they're mature, more confident, experience, and provided stability.
but how much older is considered "old" i'm dating a guy who's 3 years older.. well in actual fact 2 and a bit.. but still! =P its not that its immoral to date older people.. but as the age gap widens then things start to get complicated.. pressure for sex.. time to spend with each otehr.. interests/ hobbies.. etc. liek pervious posters age doesn't matter if you can overcome the gap and develop a healthy and stable relationship.
i think that it might make a difference if you're like young but when you get old, it might not really be that noticable.