Age doesn't matter. When I was a junior I dated a grad student, and I was friends with a couple where he was a senior and she was a freshman. If you like each other, go for it.
The only potential problems are if one party is under the age of consent (and few college students are), or if one party is 21+ and the other isn't, and the one who's 21+ wants to go out drinking and the other can't come along.