Not sure I can agree with GTA V being overrated. Oversaturated, maybe. What I mean is that if the previous GTA games hadn't been made, then V would have been mind-blowing, genre-defining stuff. The thing that still impresses me about GTA V is the detail of the world. I still think it's something that's yet to be matched. It's as close to a believable, lived in place as there has been in a computer game, and it's the scale of it without it feeling like a generic cut and paste job in the variety of the landscape from macro to micro level that's impressive. No two houses are the same, and you can instantly tell what part of the huge map you're at just by looking at the street. A massive amount of work went into GTA V, but for some reason, its games like Uncharted 4 that will get mentioned first when it come to detail and world building and as a technical achievement.
To me, there's no better 3rd party developer than Rockstar. If anything, it was GTA IV that was the disappointment. I feel they tried too hard to push the technical envelope for what was possible at the time, and the rest of the gameplay suffered. Sure, it pushed the boat out in that regard, and it was a massive step up from previous GTA's, but they went too far in trying to ground it and sacrificed some of the more satirical and fun stuff from the likes of Vice City and San Andreas. Good game, but not deserving of the praise.