From what I have played of the first Thief, its sound design, humour, and mechanics are utterly brilliant and deserve a massive load of credit considering how ahead of their time they were.
I cannot yet give an opinion on the Hitman games, but I have all of them ready to play and will have an opinion formulated soon.
i am definitely going to disagree with Mark of the Ninja and Deus Ex: Human Revolution. Though the former felt fairly intriguing, I couldn't stand its Penny Arcade-esque guard enemies and janky controls. I didn't get far, mainly due to my frustration over how there was no clear rhyme or reason to the nature of the guards. I would hook up to a high spot only for a random alarm to be set off without any degree of light shining on me, or a guard would stand in one position for literally five minutes as I traversed the area, and the moment I would get behind him he would turn around.
And returning to what I mentioned earlier...why on Earth would Klei decide upon such an absurd design for the mortal enemies of a ninja clan? Their lines were overwhelmingly cheesy and voiced with the goofiest voice acting ever. It entirely dampened the atmosphere that the rest of the game had built up so well. If these guys were perhaps other ninjas or simply more intimidating, I could take the whole thing more seriously and actually play through it. But no, just...no.
Human Revolution was a stellar game concerning dialogue, exploring the hubs, and investigating seedy night clubs and drug dealers...but the moment it would come to sneaking through a room full of military drones, everything fell apart. it felt so wooden and stitched-together.
Generally, I enjoy taking the stealth route in games that provide you with multiple options. Dishonored is at its best when you're either avoiding absolutely everybody and not laying a single hand on another human, or dropping hundreds of feet to sink your blade into a dude's throat. The level design, lore, and mechanics are all so perfectly crafted and there's just a wonderfully dynamic feel to everything. Fantastic game no matter how you slice it.
Far Cry 3 is a *much* better game when you devote as much time to stealth as possible. It's necessary towards the beginning, but few other games have ever provided so much steady development and empowerment to the player over time as FC3. By the end you're not fighting enemies as a necessity, you are the King of the Jungle and anybody who sets foot within your domain is your very, very unlucky prey. Such a satisfying first-time experience.
Arkham Asylum was a reasonable stealth game, but Arkham City definitely set it up a notch. Gameplay became perhaps more visceral and calculating, with gun-toting enemies able to mow you down the moment you see them. There was an enormous arsenal of tools that became really fun to implement into your predatory adventures, like throwing ice grenades at a dude and then ziplining at him and kicking him in the face.
They may be stat-based, sure, but the stealth components of Oblivion and New Vegas are superbly entertaining, particularly NV. Once you reach a certain level in Oblivion you can repeatedly sneak attack an enemy without being detected, and the variety of weapons and approaches in New Vegas cement it as the most viable RPG playstyle I've ever taken on.
EDIT: Improved overall use of vocabulary. I can hardly believe I pride myself on my writing abilities.