I've yet to play a game where my opinion completely shifted from hour 10 to hour 100. You can review a game in 10 hours, even less. In 10 hours you experienced most things: you know how the writing is, you're familiar with the artistic direction, you've heard 10 hours of the soundtrack, you understand most of the gameplay mechanics and experienced most of the gameplay loops, you know how it feels to drive, to shoot, to level up, to die, to craft, you already know if there is consequences to your actions or not. 10 hours is more than enough, especially if you're playing video games for some times or as a living. You don't have to finish the game or to "see everything" to have a reasonable and meaningful opinion. Same with a book, sometimes you can tell the book is great or awful with the first chapter, even the first paragraph (and even, sometimes, the book cover, I might say).