I guess any niche related to products or services that arouse interest of people during next 10 or 20 years are good niches.
I'm not sure if MMO will be a great niche during 10-20 years, but I'm sure that many people will need "credit", "loan" and "insurance", for example. BUT those niches are more and more competitive, so you need:
Find micro niches not so competitive;
Create something really different and useful.