Frankly, I've never had good naan in Singapore or even India (Bangalore, Delhi), but I haven't explored those places as much as Japan. I guess it depends on what you are looking for, but Japanese naan is huge and fluffy. There are tons of Indian people in Japan, even in small cities like Gifu, and all the restaurants tend to be family style affairs (as opposed to China, where the cook is probably Chinese...grrr....).

I'm not really a big fan of central Asian naan (too hard, not fluffy), but we have a local variation of that here from Xinjiang.