I also enjoy stealth, but a decent number of gamers who follow action-adventure and RPG's look to also master combat strategy and techniques, so there's a pretty good call for that in most games.
I had difficulty with the stealth system early in the first game and as a result started to rely more on the other special ability skills early on (kind of odd considering the game is touted as a "stealth/action adventure.) For what ever reason, I didn't find the story all that compelling, so never went back for a second game play. I did think the base plot was really original, but got tired of the style they used for the dystopian settings.
I haven't given the second game a chance yet, was on a cyber-junk jag for awhile before our move so didn't get to it.
Will have to give the Hitman series a go, it's been recommended before.
Stealth-wise I still have guilty fun with the Elder Scrolls game due to the OP stealth system. Always cracks me up when you hit a bandit with an arrow right in the butt when stealthed and they say, "Hmmm, must have been the wind.." (gives a whole new meaning to "breaking wind.")