In this article it discuses vendors and technology used in nintendo's GBA game systems. Currently this appears to be EPROM, the size limit at the moment is 64Mbit (8M bytes) however 256Mb memories will be and 128Mb memories are available. It appears Nintendo is looking at a new flash type technology for there Memory needs for the GBA.Artical on Nintendo's memory As far as I know the carts can have a maximum of 256M bytes (which is a LOT of memory). I wonder if we will see FF7/8/9 on the GBA next? 
Cyb
Cyb