arent wii games only single layer dvds? (I may be wrong though) an xbox has 8,5gb and ps3 has up to 100gb per disk so more room for larger environments, so more areas, so a longer game is possible. Just like it was psysically impossible to release gta on a gamecube
A longer game is 'possible' but certainly not guaranteed. With games taking several years development time there's always a limit. Would you rather have 5 hours of excellent story, or 10 hours of drawn out plot? Are all games (use RPGs if you prefer) on the PS3 and Xbox360 longer by virtue of having more storage available on the disc? Final Fantasy had exceptional depth and survived (and prospered) on the PS2 for half a decade. I doubt you'll find many titles that exceed it in length and quality on blu-ray/etc.