At least 15 open world video games come out every year, and I can usually count the ones worth completing on less than 5 fingers. Many open world games don't take advantage of the format properly. They'll have monotonous travel, wasted space, boring combat, and side-missions that merely exist to kill time.
Horizon: Zero Dawn has none of these issues. It's one of the good open world games.
Since you're living on a continent inhabited by ornery robot dinosaurs, combat is frequent and difficult to avoid in Horizon. Fortunately, the freedom and number of options for fighting are so numerous that you can engage the enemy any way you want.
I preferred stealth for the first half of the game, placing proximity-based explosive traps around a target, sneaking up to them and delivering a powerful stealth attack. If that didn't take them out, they would give chase directly into those explosive traps. Playing as a silent hunter is also assisted by an easy to explain stealth meter that tells you if you're visible or when your footsteps are making noise.
However, you will often be thrown into situations that force you to go loud. Shooting things with a bow is satisfying, but the game quickly gives you the really fun toys. Arrows that inflict burning, shock, or freezing effects to target. Weapons that use pressurized air to blow off components of your robotic enemies. My personal favourite is the Ropecaster, which lets you tie down larger enemies so you can focus on their weak points or pick off their lackeys. Realizing that I could also tie down flying enemies to send them crashing to the ground was a delight.
All of this combat is made even better due to the varied cast of robot dinosaurs you'll fight. You could just blast them to pieces with explosives and arrow damage, but the game really shines when you memorize their weak spots and exploit them. It's easy to take down a Lancehorn through sheer damage, but nailing a Freeze Canister on their back will cause them to take massive damage in one shot, freeze, and freeze everyone around them.
Combat is a thrilling dance of dodging, swapping weapons on the fly and trying to get that one perfect shot on a weak point. Against machines, at least. Human enemies are a bit bland to fight.
Horizon does have a fair amount of side content to complete, but because this is a Good Open World Game very little of it is filler. I wasn't particularly compelled to do Corrupted Zones or Gang Hideouts (beat up robots & beat up humans, respectively), because there was always something more interesting to do around the corner. I enjoyed completing Weapon Tutorials which teach you how to effectively use a new tool. I spent plenty of time climbing up ancient ruins and mountains to find vintage coffee mugs a.k.a. "Metal Vessels".
Also, many of the sidequests are accompanied by unique, fully voiced characters. They provide more context and humanize this sci-fi setting, and I would go out of my way to do more quests just to meet people. And many of these quests started chains where you could follow these individual stories even more. It's miles above the typical filler quests in other open world games.
Finally, the story. It was fascinating watching the mystery unravel. There's a very good reason why the game is set in the past Earth but there are robots and other incredibly advanced pieces of technology lying around. The plot starts simple, and slowly morphs into a mystery about who the main character is, and what exactly is up with the state of the world.
Finding out why is half of the fun, and I got to a point in the mid-to-late game where I was ignoring sidequests and barreling through the main plot because I was totally captivated. It also helps that there's some fantastically subtle capital-A Acting from all the characters in the game, from the inflection in their voices to highly detailed facial animations. It is definitely one of the better game stories of 2017.
Horizon Zero Dawn is visually beautiful. It has an enthralling plot and a huge list of sidequests that are enjoyable and rewarding. The world is so well designed with item and quest placement that I avoided fast travel for most of the game. The combat against robotic enemies rewards precision and quick thinking, while being flexible enough to let you play how you want. It even has good stealth mechanics!
In summation, Horizon Zero Dawn is one of those Good Open World Video Games. I don't regret any of the 50 hours I spent in its world.