It's just like any other game that's gotten 10's--there are going to be faults (sometimes big ones) but it's a testament to the strength of the developer if they can make you adore it so much that you don't care.
Take, for example, Ocarina of Time. This can actually be compared quite easily to GTA, as its' main draw was the large, near-seamless world. In Hyrule Field, there was usually no other life in this massive plain except for enemies. You could ride a beautiful horse out in this huge place, but when you ran into said enemies, you'd have to get off to engage them. And then, of course, there's Mrs. "Hey! Listen!" herself, Navi. But the fact was that the rest of the game was so flawless, such a masterpiece, that these flaws that may have crippled a lesser game went virtually unpunished. Maybe GTA IV is one of said masterpieces?
I've been thinking for a while about the topic for my first VGC feature--I think I just found it! Thanks, KoW