Absolutely nothing like we would know.
The GTA franchise is one of those that's responsible for some massive technological/design-advancements in our industry. Without GTA, we'd probably be set back 5 - 10 years in terms of design and technology.
I can't imagine it would be anywhere near as good as GTA V, simply because our rendering technology would not have gone through the necessary iterations of dealing with open world design issues, and the gameplay would be poor as the designers wouldn't be as experienced as they are now.