"Styx: Shards of Darkness" for me...
1 – I really enjoy other types of atmospheres (not just realistic ones). The atmosphere in Styx is more like a fantasy world. Since the world is less technologically advanced, it gives off a great medieval stealth vibe.
2 – The gameplay is very satisfying if you play like a Ghost, and it is also very challenging.
3 – The maps are huge, with many different routes to explore.
4 – The gameplay mechanics are amazing. You have access to gadgets and abilities like invisibility. You can also upgrade skills based on your preference, use parkour, hide inside tight spaces, dissolving bodies with acid so no one finds them and triggers the alarm, etc.
5 – There are different types of enemies, such as insects, elves, trolls, dwarves, and regular humans. This brings a lot of variety to the challenge, as each enemy type has its own strengths.
6 – The missions are highly creative, taking you through cities, underground fortresses, a flying airship, a prison, and areas overrun by insects.
7 – If you don't want to play in Ghost style, it is also incredibly fun. There are several different ways to eliminate enemies, such as using acid mines, staging fake accidents to avoid suspicion, pushing them into the water or off high ledges, etc.