Does that include FFXI and all the expansions?  Would the FMV's be left in SD or be redone in HD?  Even so, they would probably all fit.

That would be one amazing package. I can imagine SE chargin upwards of $250 for it though.

Easily and with space for more games left

The N64 had an average of less than 50MB/game. To make it easy, we'll say 50MB.

There are 410 games on N64. That's 20.5 GB. Realistically, 15 GB, maybe 10.

Most PS games used 50MB game. For all the games, you'd need ~ 60 GB.

The entire 5th generation could fit on 2 blu-ray discs.

For FFs.

FF 1-9 should take up nothing (you could put that on a Ps2 disc).

The 4 large ones on Ps2 could take 4 GB each. So 16 GB there. If you're going to put the FF CC ones on, 20 GB total.

Overall, 25 GB should be the max. Half a disc.

Your number for the size of PSX game are completly screwed, N64 games took a lot less place than PSX one. They were some RPG on PSX that took upward to 4 disc, you think it was for fun? No they needed the space, all the main serie FF game on the PSX took at least 1GB of space. I don't think there is a game as small as 50 mb for the PSX.

Easily

I'm going to say no, simply because everyone else is saying yes.

The Nes and Snes Final Fantasy's had batteries inside of the cartridge. Where would you put the battery on a Blu-ray disc?

Blu-ray=fail

As long as we're talking about actual disc/ROM images, then you should be able to fit them all into a 25G Blu-Ray disc. However, knowing Square-Enix's propensity for bloated remakes, you would probably need at least two 50G discs for VII-XII alone.

Without any problems actually. A dual-layer one that is, I'm not sure that 25 GB's would cut it in the end.

It could be done but it would be a cold day in Hell before they ever actually did it.