TL;DR: possibly the best open-world action-RPG I have played. If you have a PS4 and like open-world action-RPGs, buy this. If you don't have a PS4 and like open-world action-RPGs, you may want to get one; it's that good. I finished the game and immediately started a New Game+ so that I could re-run the early game dialogue with the full story in mind. (Spoiler post coming later, because I really want to talk about the worldbuilding and story.)
Trailer
The open world design is great
The various zones open up in a natural progression, starting with your tribe's inner lands, then you leave into the wilder hunting lands, and eventually progress into other tribes' areas. The map is huge and varied, with beautiful terrain that ranges from woodlands to snowfields to desert.
It has the Ubisoft-style "climb towers to reveal the map" mechanic that's been around forever (I first encountered it in AC2), but instead of tall buildings or radio towers (which in Far Cry 3 always frustrated me by being platformer puzzles, so in FC4 I got good at landing the minicopter at the top instead of climbing the stupid things) they're giant robo-dino-giraffe things and the tricky part is figuring out how to get to the jumping-off point safely and then timing your jump onto it. Once you're on its back, it's a simple climb.
The visuals are amazing
Even on a PS4 non-Pro. the graphics are absolutely stunning. Mountain vistas, creature design, weather, flowing water, grass blowing in the wind...it's all there, and there's a photo mode so you can tweak a still shot if you want stunning desktop wallpaper....
Combat is good (ranged great, melee meh)
There are a wide range (heh) of ranged weapons; several bows (with specialty arrows for each and tradeoffs between range/rate of fire/damage), two slings (one for bombs and one for elemental damage), a tripwire-launcher (possibly my favorite), and a rope-launcher for tying down enemies so you can bash on them.
There's basically one melee weapon with a "light" and "heavy" attack, though the light attack can do extra damage under the right circumstances (stealth, downed enemy, attack from above, etc) if you have the skills to go with it. Mostly it's "go in, swing, dodge, swing, oh shit oh shit run".
Mission design is really well done
The main missions do have placeholder tasks throughout (find your gear, go here, go there, talk to Bob, exit the gate) but in those cases there was generally useful and interesting background dialogue to build the world/progress the story. The main tasks are a nice mix of combat, puzzle, exploration, etc.
Few of the side missions (usually a short chain) include fetch quests, and they're mostly "bring me the heart of the giant beast over there" rather than "bring me 20 bear asses" (TVTropes warning). (One of the earliest ones is a "bring me some rabbit meat" one, but that's practically a tutorial mission anyway....) Some of the sidequest givers are also really well done minor characters who I wish I could see more of; it's worth going back to cycle through their random responses, in many cases.
In almost all cases, it's possible to tackle any given mission/monster/etc in different ways. Combat types might just rush in; sneaky snakes can hide in tall grass and use stealth takedowns; trapmasters will set bombs and watch the fireworks; snipers will sit back and headshot. Or one might use a mix of those.
The writing and story is absolutely amazing
To the level of "this is getting one of my Hugo nomination slots next year" (as a Best Dramatic Presentation (Long Form)). The dialogue is great. The datapoints scattered throughout the world are great. Characters. Plot. Everything. The latest patch adds a "Story" difficulty to make combat no longer a major issue.
Trailer
The open world design is great
The various zones open up in a natural progression, starting with your tribe's inner lands, then you leave into the wilder hunting lands, and eventually progress into other tribes' areas. The map is huge and varied, with beautiful terrain that ranges from woodlands to snowfields to desert.
It has the Ubisoft-style "climb towers to reveal the map" mechanic that's been around forever (I first encountered it in AC2), but instead of tall buildings or radio towers (which in Far Cry 3 always frustrated me by being platformer puzzles, so in FC4 I got good at landing the minicopter at the top instead of climbing the stupid things) they're giant robo-dino-giraffe things and the tricky part is figuring out how to get to the jumping-off point safely and then timing your jump onto it. Once you're on its back, it's a simple climb.
The visuals are amazing
Even on a PS4 non-Pro. the graphics are absolutely stunning. Mountain vistas, creature design, weather, flowing water, grass blowing in the wind...it's all there, and there's a photo mode so you can tweak a still shot if you want stunning desktop wallpaper....
Combat is good (ranged great, melee meh)
There are a wide range (heh) of ranged weapons; several bows (with specialty arrows for each and tradeoffs between range/rate of fire/damage), two slings (one for bombs and one for elemental damage), a tripwire-launcher (possibly my favorite), and a rope-launcher for tying down enemies so you can bash on them.
There's basically one melee weapon with a "light" and "heavy" attack, though the light attack can do extra damage under the right circumstances (stealth, downed enemy, attack from above, etc) if you have the skills to go with it. Mostly it's "go in, swing, dodge, swing, oh shit oh shit run".
Mission design is really well done
The main missions do have placeholder tasks throughout (find your gear, go here, go there, talk to Bob, exit the gate) but in those cases there was generally useful and interesting background dialogue to build the world/progress the story. The main tasks are a nice mix of combat, puzzle, exploration, etc.
Few of the side missions (usually a short chain) include fetch quests, and they're mostly "bring me the heart of the giant beast over there" rather than "bring me 20 bear asses" (TVTropes warning). (One of the earliest ones is a "bring me some rabbit meat" one, but that's practically a tutorial mission anyway....) Some of the sidequest givers are also really well done minor characters who I wish I could see more of; it's worth going back to cycle through their random responses, in many cases.
In almost all cases, it's possible to tackle any given mission/monster/etc in different ways. Combat types might just rush in; sneaky snakes can hide in tall grass and use stealth takedowns; trapmasters will set bombs and watch the fireworks; snipers will sit back and headshot. Or one might use a mix of those.
The writing and story is absolutely amazing
To the level of "this is getting one of my Hugo nomination slots next year" (as a Best Dramatic Presentation (Long Form)). The dialogue is great. The datapoints scattered throughout the world are great. Characters. Plot. Everything. The latest patch adds a "Story" difficulty to make combat no longer a major issue.