An older boyfriend or girlfriend can be great: he or she is more developed physically, more mature, wealthier (maybe), he or she can drive... Unfortunately, older boyfriends and girlfriends are usually looking for just one thing: sex, and they're less hesitant than their younger counterparts to get it.
Of course, not all older guys and girls are looking to score. However, most older people who treat their boyfriends and girlfriends well are dating someone their own age. Truly mature older guys date mature, older girls, and vice versa. Your best match is very likely someone your own age. Besides, it's hard to date someone three or more years older simply because of the experience gap.
There are some younger/older relationships that work. Unfortunately, most don't.
Some college students compete to see how many high school kids they can get. Of course, they're very sweet about it: they'll say how pretty you are, how much they like you, how special you are, and they'll buy you nice things, and maybe even say they love you-- but if you don't give them action, they'll start to complain. After all, it's not you they want; it's what they can get from you.
Is this the kind of relationship you want? Tell these jerks to take the hike they deserve. Look for a sweet person closer to your age. You'll be much more successful.