Thief series. They are a RPG experience in the sense you really have to get into the role of Garrett the Thief in order to complete the game on hardcore mode (no kill, no alarm, and on some missions like the sheriff safe heist no KO). I remember spending long minutes in a dark corner listening to guards walking in different directions around me (one of the best game audio in history, by the way) in order to "see" their patterns and avoid them. Enjoyed getting on the rooftops in the 2nd game and getting the vibe of the "thief highway".. Looking Glass games were the most immersive, and Thief series were the most immersive of Looking Glass games. If you havent played them i recommend the modernized versions that are floating around, and the 2nd game has probably one of the most epic endings ever...
