Comparison about gameplay value, not realism. Physics, gunfight, AI, melee combat, controls, interiors, multiplayer freedom. While GTA V has some obvious advantages from being a 2013 game, a lot of technical features and sandbox elements from GTA IV (2008) were missing such as crouch ability, holding onto ledges, picking up objects and much more. Those changes reduced all the unpredictable fun and made it an experience with less replay value.
No mods were used, this is the original version of both games on PC. Cheats were used at some point for demonstration purpose but every comparisons are fair to each other.
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After Dark / アフター・ダーク by NoGht
TBOGT pause menu
GTA IV Soviet Connection (mixed Intro)