They seem to all (?) use the same database at ramendb.supleks.jp. That being said, I've decided I like 「ラーメンマップ」by YSS at Tokyo. I may continue looking, because I'd really like to be able to do more results filtering (like, for example, only show me tonkotsu places?).

And no, it's not just restaurants in japan! It shows restaurants in america, too! O_o