Honestly, there are very few games I would rate at 5 stars. Off the top of my head, I can only think of 4 games in the last ten years that I would give that rating to.
Also, I'm not typically a fan of Ubisoft anymore. They freaking nailed it this time. The game is so beautiful and detailed! The story so far is fantastic! In my opinion, the game is sort of like RDR2 but on Pandora. I say that solely because I could hunt, gather, and just explore the game world forever.
The VA gets some criticism online, but I didn't think it was bad personally.
The story was fun (so far, haven't finished it yet) but I've logged an asinine amount of time just roaming.
Tons of content. I mean tons. The map is huge and filled with danger, and fun!
The game doesn't explain everything though. It doesn't do a lot of handholding.
In my opinion, it's a must-have game, and easily a contender for GOTY.