Do not trust the user average, this game is a 9.5 at the very least. Best game in around 10 years, a unique experience.
With that cleared, I will now tell you why DS is a game that every single gamer should play.
For starters, the game is extremely solid in all aspects. In the graphics department, while it isn't presented in the best definition (console port - fix with mods if your PC can run them), the graphics match the setting extremely well. Locales are interesting, colouring and scenery ranges from the mundane to the epic, and it gives a feeling of solitude that goes very well with the whole ambience Fromsoft tried to create. Sound and music, while the latter is scarce, follow the same line, and in particular the sounds of combat convey the weight or speed of the weapons used and the power of the enemies very well. All of this contributes to create a thrilling atmosphere.
From a gameplay standpoint, the basics are simple enough, few keystrokes are required to use your character to the fullest, and navigate the various yet simple menus, this is also extremely consolized, but again mods are helpful with interface gripes. Combat is fluid and extremely varied, each and every single weapon has a unique moveset, which you end up mastering through experience, which means re-playing the game with a different weapon can be an extremely different experience. The use of magic and ranged weapons are also unique systems and very fun to use, giving a completely different feel on the same fights you had already visited with a different character. Armor is extremely well implemented, affecting not only your resistance, but also your ability to dodge attacks and run at higher speeds, while the same tougher armor will make you more resilient to damage and allow you to avoid getting stunned by enemies.
Character creation is simple, but any class you choose at the beginning can become anything as you level up and increase your power by collecting souls from enemies when they're defeated. You can build so many different characters I could write pages upon pages of content solely on that topic, from a one handed quick dagger user, to a mage, to a spellsword, to a massive tank, to a more agile and well rounded character, to a cleric versed in healing arts, a character based on getting backstabs and parries, you name it. And I also guarantee all of these can get through the game.
Difficulty in this game is an odd beast. At the start of the game, you will feel absolutely trashed by the simplest of enemies, I cannot remember how many times I was killed by simple rats during my first moments with the game, the second boss took me around 20 tries, and the third around 40 in total. However, learning and investing time with the game is highly rewarded. By the time you try your hand with a second character, you'll see how you easily breeze through the same parts that had you in huge problems before, and that feeling of being rewarded for learning the game is one of the better aspects of this game, that very few manage to achieve.
Finally, many people will tell you DS has no backstory, but the truth is the amount of lore to be found is absolutely enormous. The world is rich and characters are deep, but you must be very thorough to get all the details, which are mostly stored in conversations, corpse locations, and item descriptions. Much of the story is open for interpretation, which makes for interesting theories that circulate in the very hardcore DS community.
As for negatives, I'd say there's 2 "big" ones that don't diminish this game's quality in the least. First, the port is not really good at all, it doesn't use the PC's capabilities appropriately, this is easily moddable. Second, the absolute lack of a real tutorial, or a useful manual. It took me several tries to discover what a shield's stability meant, and what each stat did for me, or to find out how to use magic, things like these shouldn't happen.
This game really grows on you, it's a deep and compelling game, with great story elements, but the best part is by far the extremely flexible character system, and the ridiculous replayability. Oh on top of all, this game has an awesome co-op multiplayer, despite some server issues.
10/10, 100%, A+ game. Dark souls 2 has ridiculously large shoes to fill.