If something feels biggers than it doesn't matter if it's bigger in reality. The feeling is all that matters, and R* in 2004 on PS2 definitely pushed the limits more than they did now with GTA V.
Yes. Also much features that were planned to be in San Andreas, or they exited only in beta, were deleted because of PS2 limits. You can also see while browsing San Andreas files, remains of that things. Like skateboard, animations for animals, San Fierro Rifa tags, Alcatraz, etc.