Yeah, it is a pretty big difference. But it makes sense that if people are sorted by their personalities, the distribution wouldn't come out totally even, so I like that we have tiny group of Gryffindors for this year. I'm sure that it evens out somewhat across the seven years of students, and their common room is just as full as anyone else's.

Neville did mention that the Gryffindor boys are particularly close friends, and I'd bet that the smallness of their group contributes to that.