Sleeping Dogs does, at first glance, look like an open world GTA clone, and while there are similarities between the two, the games have a very different feel to them.
Story & setting
In Sleeping Dogs you play as an undercover cop, who has to infiltrate the triads in Hong Kong. While the core story itself might be nothing to write home about, most of the characters, even the ones that you are supposed to dislike, feel like they have have reasons for what they do, things that motivates them on a personal level. This is in particular true for the first part of the game, where the story has a rather personal tone to it.
Sadly as the game's story expands, to cover events that does not just deal with the starting part of Hong Kong, the story goes downhill. Less time is spent on each character, which means that only a few are given enough screentime for proper character development. The later parts feel rushed, and not nearly as well thought out as the early parts.
There is also a dating part of the game. Something that very well could have been an interesting addition, the main character is after all an undercover cop in the triads, and letting the player try to deal with his personal life at the same time as he tries to take down the triads could well have been an interesting thing. Sadly, this feels incredibly underdeveloped, as each girl is given a single "quest" for you to do, and instead of having the characters connect on some personal level, you are given a reward in the form of map markers showing up for particular things (depending on the girl). And you'll have the option to "date" all of the girls, with no repercussions, in fact the game encourages it, and only once is it mentioned that one girl might not like it (but as you don't see her ever again, it does not matter anyway).
The city itself feels relatively large, and there are plenty of people out an about, which makes the city feel alive. Sadly, there are not enough for it to feel like it has the population of the actual real world city, but even a high end PC would probably have trouble with actually having so many NPCs.
The core gameplay is surprisingly solid in Sleeping Dogs, in particular the melee system. The main character has several different "moves" available, and more are unlocked as the game progresses. From simple punches & kicks, to throws, jump kicks and counters. And the combat flows really well, giving it a very good "feel". It really does feel like you are in almost complete control of the character.
The gunplay is considerably worse, but still not bad. It works, but many games have done it better in the past.
And even the driving controls work (much unlike how it is in Saint's Row 2, where driving in the unmodded game is painful).
There are several different ways for the main character to grow stronger. After each mission you are given two types of experience, one for the "cop" side and one for the "triad" side. These are not mutually exclusive, instead the potential "cop" experience starts maxed out at the start of each mission, and any bad thing you do will lower it (this includes stealing things, hurting or killing civilians or property damage). Triad experience is earned as you deal with enemies, and the better you do it, the more you get (a headshot is worth more than just killing the enemy by shooting it repeatedly in the foot). The cop experience encourages you to actually behave like a human being, and not just drive like an idiot, while the triad experience encourages good use of the combat system.
There are also collectibles in the form of jade statues & health shrines. The statues are used for learning new moves from a martial arts instructor, while the health shrines increases maximum health. Sadly these two (the shrines in particular) feel rather "gamey", and immersion breaking. Cruising around, looking for shrines to pray in front of in order to increase max health just does not feel right, and detracts from the overall experience. There are also other minor collectibles, but these feel more optional.
There are no shortage of sidequests either, both in the form of missions to help hte police and those that helps members that in some way are related to the triads, and the rewards for these is experience. Also, there are street races & fighting events, both of which feel appropriate in terms of how they are presented.
Even on my aging computer, the game ran just fine, and it still managed to look pretty good. There were a few bugs here and there, but I did not experience anything serious. The worst thing that happened was when a boat I was in suddenly sunk right at the start of a mission, which forced a reload (as I died due to this). But apart from some minor oddities, the bugs were relatively far between.
This is a console port, but it is a good one. The controls do feel rather "consoley", but they are not bad.
The DLC for this game deserves a special notice. There are plenty of it, and most of it does not really matter. Some add some new fighting styles, but as I don't own those, I can't comment on them, and some are just cosmetic. There are two pieces of free DLC as well, one of which adds high res textures, and the other give you some more hats.
Then there are the story content DLCs. These give you stories separate from the main game, but one of them is played during the course of the main campaign. The Zodiak tournament can be accessed at any point during the main campaign, but it is recommended that you do it late during it, due to the challenging combat. Nightmare in Northpoint give you a rather strange story about the walking dead that has an entirely different tone than the main game. Both of these are worth buying on a sale, but they are short. I can't comment on Year of the Snake, as I've not played it.
Be warned that there is actually some cheat DLC for this game, and unless you want to make the game easier, avoid these like the plague. These are not properly marked as cheat DLC though. The cheat DLC include: Top Dog Gold Pack, The Red Envelope Pack, The High Roller Pack & Top Dog Silver Pack. These mean that it might not be worth buying any complete DLC packs, as you really don't want to have them (Deus Ex HR had the same problem as the Tactical Enhancement Pack was a straight up cheat DLC, giving you a lot more money and two extra weapons)
Overall Sleeping Dogs was a really good game. It lost some steam towards the later parts, but it still remained fun. It was also somewhat lengthy, at 23h (and I did not do everything). This game is strongly recommended for anyone who have even a slight interest in these types of games.