GTA IV was a port of the XBox360 version which has 3 CPU cores. GTA IV was the first triple A game that maxed out all three cores. Most PCs at release time still had dual (2) cores albeit a lot faster cores than the XBox360. So GTA IV never run fine on a PC with just two cores.

Another thing was the bad driver compatibility with ATI/AMD graphic cards. For the nVidia cards there was the first time ever that they released a special launch beta driver specially for GTA IV PC.

Beside that, to run at very high settings one needed a high end graphics card. GTA IV was with Crysis 1 the last PC game that pushed hardware to the limits. Even today both still look great, and with certain mods they look as great as GTA V (though in the later case the engine is more optimized). Nowadays GTA V is a XBoxOne port and it doesn't push the PC hardware to the limits, it uses just 25% of my CPU and 50% of the GPU running with 60 fps in 1080p.

Part of releasing any game to a set of hardware should address the question "what type of systems are actually in the hands of our users?" and making the game run well at all of the settings the game supposedly offered. GTA IV failed at scaling down to the minimum (or even "medium") requirements they listed.

If you're releasing a game that only works well for next-generation specs but advertising current generation support, you get the reputation you deserve.