Well Tales maybe for third but it wont sell so well.There is lot of those that are great JPRG games but wont just sell.

Pokemon sales>Final Fantasy or Dragon Quest

To answer you question; Jrpgs are pretty niche outside of Japan. I guess most Westerners have different tastes than the Japanese. Same reason FPS don't sell to well in Japan.

Tales sells well(in Japan anyway) and Star Ocean sells pretty well, and Shin Megami Tensei does well for an Atlus series

Brandname is everything.

Particularly in JRPG ...

FF and DQ, big brandname...
Name has alot to do with some things.

How many copies does a JRPG have to sell to be successful? FF need to sells millions while Tales, Shin Megami Tensei, and Star Ocean only need to sell a few hundred thousand to be successful. Success is not determined by the number of copies sold but the amount of profit made from the sales

EDIT:The 'a game has to be brand name to sell' thing only applies to Japan. In the West, a JRPG or any game selling well depends on the amount of marketing it gets

OH and kingdom hearts is at or close to the FF, DQ level as well. I wonder if there will ever be a rival to pokemon. ;) Right now nothing comes close.

Cant just count pokemon as JPRG...Just cant.......Never.......

Why can't you? It is by definition a Japanese Role-Playing game. What genre would you list it as?

...Adventure-action....