If it helps, that gaming wikia's sizing of Red Dead Redemption needs more refinement.

I spent a lot of time doing the math on Red Dead Redemption years ago in GTAForums, and my numbers should hold up to any kind of test you can think of using in-game travel stats. The "whole map" that you see in the map view of RDR is a rectangle that's about 15 square miles. The "playable" area, the boundaries Marston is supposed to keep inside is about 5.75 square miles. That's surrounded by inaccessible terrain you can see beyond the boundaries. All of the terrain in RDR, including everywhere you can see but can't go, is 17.4 square miles.

Your numbers suggest Spider-Man could be about as big as GTA IV. The gaming wikia's is about right for that one. That number represents a rectangular area drawn around GTA IV's islands. The area in that rectangle is almost precisely half land, half water. If Spider-Man offered about 3.4 square miles of web-slinging area, that would be equal to the urban landmass of GTA IV.