Questionable posting about any of this stuff here - definitely dancing on the line w.r.t. da rules.
For anyone who is curious, though, these 40GB figures you keep seeing are for all ROM's from the mid-90's and below. Once you move into the PS1, you start looking at >1TB for each region uncompressed. Gamecube is 1-2TB uncompressed for everything. I think PSP is similar. Encrypted 3DS dumps end up being about 1TB, I think.
Formats start to get weird from the Wii on up. On the Wii specifically, discs are filled with algorithmically (sp?) generated garbage data, so they are difficult to compress without trimming. Archiving nerds will need to make tough choices, there. WiiU uses some weird file formats for eShop games I haven't looked into too much... good luck finding disk dumps.
Haven't messed around with Xbox 360/PS3 ISO's but they are out there. No Datfiles for consistent naming, though. You will need to make one yourself. 3DS datfiles are also missing the vast majority of updates and DLC.
You will be needing some pretty serious storage tech if you actually want to keep all of these locally, reliably.
Random brain dump for you there.