For all the increased focus on plot and character in GTA, I don't think the protagonists are meant to be iconic characters as much as representing familiar archetypes from movies and TV that are relevant to the chosen setting.
Did you notice the Lara Croft chart comes from a costume resource? Tank top and shorts in the v1 colors and gun holsters in combination go a long way for a Lara costume (I always felt that getup was meant to be a 90s 'hip' version of Indiana Jones' hat and whip).
It would take a very discerning eye to recognize most GTA-themed halloween costumes, I think. If anything people would more likely recognize the 'original' guy from Miami Vice, Boys'n'the'Hood, Heat or Sons of Anarchy they seem to be modeled after.