I know being objective isn't possible in art criticism but still, GTA V being superior compared to GTA IV is the closest thing you'll ever get to an objective analysis for a video game case. Every gameplay element in V is just better compared to IV. Shooting has been made responsive to the point it actually becomes enjoyable to finally engage in gunfight. Physics has been finally balanced where those 'drunk' euphoria quirks has finally been toned down, thus you get to actually control your character instead of seeing him stumble down and fumble beyond your control. The setting offers diversity enough that going back and playing in Liberty City back again feels suffocating and restrictive and hampering player freedom in its topography. The level of detail is sublime nuff said.
Writing and satirical commentary has also been made pointed and directly focused in the key areas that Rockstar has made even clearer in this iteration. Now this may be a bit subjective so this is just matter of preference. Still, the hypocritical nature of GTA IV to humanize Niko's story yet still serve gameyness antics for sake of fun is a definite negative to the game's behest as it confuses the narrative and makes it clash against the gameplay. GTA V adores in its action-driven nature and while giving out fun and adventure it never misses the point it wants to tell you in the first place. The soundtrack can also be a bit subjective. But for me personally, the fact that they managed to make me aware of an even broader range of genres in music was a definite plus on their part. The serendipitous moments of me driving across town with an exactly apt music to accompany has never been frequent as it has been here in V.
There has never been a more emergent open world game that I've played since GTA V. Everything just comes together as one cohesive experience. I've never felt like it being a checkbox of sorts. *ahem* (inquisition)