Which buildings in LEGO Island 2: The Brickster's Revenge were based on real-world sets?
As the sequel to LEGO Island, many (but not all) of LI2's models are based on sets from 1998 to 2000.
Castle Island is based on LEGO Knights' Kingdom I. The castle itself, therefore, is loosely based on 6098 King Leo's Castle (my 3rd most wanted set of all time).

The battering ram shown in the screenshot is from 6096 Bull's Attack (my 4th most wanted set of all time — yes, right after the castle).

Adventurers Island is based on the Dino Island and Desert subthemes of LEGO Adventurers. The Sphinx shown in the screenshot somewhat resembles the one in 5978 Sphinx Secret Surprise.

The Spaceport is from 6456 Mission Control.

The Res-Q HQ is from 6479 Emergency Response Center.

6332 Command Post Central is split into two parts: the main police station building, and the jail &amp; helicopter/helipad.

An exception is Nubby's gas station, which is a significantly modified version of 6397 Gas N' Wash Express from 1992 which was also rereleased in 2001 with the set number 6472.

The rest of the buildings appear to be unique to the game. Not even the new pizzeria seems to resemble any of the existing pizzeria sets.