While I still like GTA IV's guns and sounds better, they weren't perfect. I never liked the muted pop or the lack of efficiency of the Glock.
Max Payne 3 pretty much nailed everything. The guns sounded, felt, and looked great, as did the gore. However, that game was rooted in theatrics, and I can't see 50-year-old wise-guys doing dives off balconies with dual SMGs.
But yeah. GTA V's gunplay isn't well-optimized. When I used to play Online, everyone would just auto-aim with an assault rifle or pick everyone off across the map with the sniper. I found it possible but difficult to hold my own with pistols, SMGs, and shotguns.
GTA IV felt more balanced and intense to me. The snipers were a bit garbage, discouraging quick-scopes and long-range dominance, but could still be effective if you weren't retarded. The Deagle and .44 packed a wallop and were relatively accurate and could be fallen back upon. The AK and M4 were practically side-grades, people still arguing which one is superior in GTA IV today. The SMGs made up for damage with high fire rate and clip size. Around all the narrow corners of LC were places a shotgun could ruin someone's day. The only thing really BS about GTA IV online was the RPG, as it is in every game.
Take the aesthetics and cover system from Max Payne, the gun functions from GTA IV, and you've got a great game. I miss when I could dominate online with nothing but a Hexer and a sawed-off... Riding a motorcycle is a death sentence in V.