I was a MAJOR fan of Thief 1 and 2. T3 was like Highlander 2: you just want to ignore that it ever existed.
This Thief though had a recipe for greatness and it did partially do the job. The levels were nice, if not consolized and thus smaller with load zones, but there was a lot to explore and find. AI random conversations were effing annoying as they had one one or two things they would say across the entire damn level. I lost count how many times I heard two guards talk about "What does third offense get you? The noose..." or "I rolled Polly Adler last night..."
Seriously, why can't companies go hog wild on random AI conversations. Dishonored did this better than most games by having random questions with random, but generic, answers.
Graphics are good, movement is good, weapons are good, and stealth is actually better than most games. It's just the finishing touches that could have fixed the overall atmosphere. Like, how can you HONESTLY steal earrings off of a person? In T4, you can and they don't notice a thing. Oh, and you can make the game as hard or as bloody easy as you want. An interesting feature, but not enough to really call it a PC game. Basically, you can edit how much HUD you see, how much the environment gives you hints to loot locations and secret stuff, and how tough it is to sneak around. I recommend taking a long look at these options because they can really help the game feel more stealthy and not give it "kiddie mode" difficulty.
Now on to the "factions". Thief 1 and 2 had incredibly separate factions with completely different ideologies. They kind of tried to do that in this game but it felt uninspired. Gone are the lovely poems of "The Metal Age" and here to stay are just dudes talking to each other like dudes. "Weather's changing..." Also, you kind of got the feeling that the City, in T1/T2, was mankind's only stronghold. Thus it was the City vs the wilderness. Not so in T4. The City, despite being called that, is just a city among other cities, among other countries. There's no reason to call it "The City" with a capital C anymore.
Basically T4 is Dishonored 2, but without magic and less moral decisions to make. (Which actually makes me happy because I hated not able to use half of my spells or gear in Dishonored to get the best ending.) Thief really isn't this way which is a relief to me. But it's Dishonored with the City, stealth, random AI talking, a plague like thing killing people, and what not. The plots are obviously different, but the settings are almost as if one company bought the game from the other and just made their own unique copy.
As a diehard Thief fan, I had to play this game. It's WORLDS better than T3, but it doesn't match the atmosphere and feeling that one got from T1 and T2. (Man T2 was such a phenom of a game.)