Why we can't have this anymore?

I think that would've been too much for the ol' PSP
SA was already pushing limits on the PS2

SA is only 3 gb

Because much better games have released since then.

Obviously it would have been just Los Santos city, even with reduced detail it would have been great.

That's what i am saying.

So what, Skyrim is just 2GB and bigger than all GTA games combined.

and psp discs were 1.8 gb

skyrim was 4gb

skyrim was 5.5 gb
but mine is around 90 because mods

shark cards are too lucrative