Map in V is definitely not the same league. It's a lot higher than SA map. Sure it was big for it's time, but small and empty cities made mostly from block like buildings, boring deserts and forest between them isn't something worth praising.
You can't say SA map was bad because of block like buildings that's not even fair you're comparing apples to oranges. If they re-created the SA map with the new engines in HD graphics it would trump GTA V by mile, at least in my mind.
Engine and graphics got nothing to do with it as GTA III and VC despite being older were much better in that departament.
I don't know if that feels is result of empty streets, lack of atmosphere or something else, but cities in SA feel dead like during outbreak of a plague. LS (districts that weren't part of the ghetto), whole SF and parts of LV outside The Strip felt unreal and fake. Buildings were there, but along with feeling it's not real, like movies props.
GTA III and VC were older and their graphics used much smaller amount of polygons, yet the developers could turn them into believable places by adding many details that simply add realism. Payphones, benches, railings and similar unnecessary for story stuff was there to create atmosphere of the real life place. SA feels in comparison like a theatrical scene, when director is trying to tell you these two armchairs and table are standing in baron's room in the big manor.
SA map recreated in HD could be much better, but it's not and won't be recreated. Such process could add details needed for realism, but how do you know what would we get if GTA III or VC map would be recreated as well.
R* decided to get in quantity while making SA losing quality in the process. Looks like they learned they lesson about this though. I personally would give half of the SA map and features for atmosphere and details creating believable places and pleasant gameplay.
It's uncanny how much we think alike. Well said.