The first one was one of my favorite stealth games. Unique stealth mechanics, unique setting, interesting characters, decision based, ghost runs, assassin runs... or you could just play it like a survival game and kill shit (though not easily, making a presence sends you down paths that makes this very hard for you). There were dozens of ways to play the game, and the entire game reacted to how you played it. Everything you did mattered, the game had actual legit replay value. It was a way more interesting version of recent offerings in the sadly underdeveloped 3D stealth market.
Needless to say I'm hyped for this. Hopefully it's as good as the first one.