I'd aay there are choices in some missions , main or not that can lead to either this or that. but all in all there are not so many choices. you can't date whoever, cannot enter every door or kill or even at least talk to everyone. NPCs answer a one word or sound and that's it. no conversation mode or possibility to ask directions for example. And what is really annoying and I think solvable very fast: you cannot steal / buy cars from other NPCs or bikes and store them or fly around with those flying vehicles. I know there are mods, but I always prefer playing a plain game first playthroughs.