Horrible controls, messy graphics, unrealistic fight prevented to enjoy the game. Driving is not fun, controls are very bad, even on foot the camera is clumsy. This is very bad point for a game where you mostly drive something. Graphics are nowehere good, not even for its age. Fight is too much easy, you can oneshot everyone while you outlast everything (except if you try to make a graffiti, then gang members come and kill you in no time). Already the opening sequence is about killing about 100 cops while making a getaway. The painting shop clone from GTA is even more hilarious, if you go in, cops forget you even if you're running with a SWAT car... This is definitely not a Good Old Game, much more fun to play GTA: Vice City hundredth time than this for once...
Thief 3 has the best story out of the three, and the atmosphere, hiding, sneaking, stealing is still top notch, in footsteps of the first two. Graphics are not bad for its age, the design is good enough to prevail and set and atmosphere. Sounds are good, voice acting is still on par and familiar for players of 1 & 2. Game mechanics are largely the same as in previous games, only rope arrow was switched to climbing gloves. The map designs allow some freedom during the walkthrough, while the player will not get lost. This can be a good or bad thing according to the taste of some, but I think it is still on the line that is acceptable for the most. And as I mentioned the story is great, sometimes referencing to previous installments and rounding up the trilogy. The only possible issue is the compatibility on contemporary machines. I hope GoG implements the Sneaky upgrade mod (https://www.ttlg.com/forums/showthread.php?t=138607), or at least it gets a sticky in the forum, because it would be a shame if someone abandoned this game only due to this.