Unfortunately, there you come to the iPhone's biggest problem, game prices. It just isn't very profitable to do big games like Disgaea or JRPG's on the iPhone, because the most anyone seems ever willing to pay is $10, and the $10 games that sell well are not common at all. For a traditional publisher like Atlus, they could have a game made for DS or PSP and make $20 to $25 on every copy sold, with a customer base of 50 to 100 million dedicated gamers, or for iPhone and make $7 on every copy sold, with a small percentage of customers interested in "hardcore" games like that. That's why you rarely see console-quality games on the iPhone - only companies like EA who doesn't really care about making a profit on the iPhone as much as improving their reputation, while having the marketing money to really get the word out about their games.
That and there are like 45 new games released on iPhone *every day* - it's very easy to get lost in all that. You need a lot of marketing, or luck, to get past that.