Gothic 2 is a deep, immersive RPG that will provide many hours of quality playtime.
The game also has a unique classing system. When the game starts, the hero is classless. Over time, though, the choices made and the way quests are completed will lead you into one of three major classes: the mage, the paladin, or the mercenary/warrior. While many of the classes have side quests in common, their ways of solving the quests might be very different. Also, some quests are only available to certain classes. The class choice does make a very real difference in how the game plays out and how NPC's react to the character. The paladin, for example, is a holy knight in the service of the king. Those who don't like the king (or the government, etc.) might attack you on sight if you are a paladin, but might leave you alone if you look like a mercenary. The combat system is interesting, if not very deep. Still, though, through different skills and different weapons, varying styles of play can be effective. Timing is a big part of combat, since parrying, dodging, and linking attacks together are all very timing intensive. Sometimes it can take awhile to learn how to best fight an enemy, and the technique can make all the difference in a fight. The world is quite expansive, and it is unlikely that a person will ever feel like there aren't enough places to explore in this game. Over time even more area open up to explore, so explorers should have a field day with this game. Also, most characters in the game are killable. I say most because nearly all are. There are a few exceptions, though, where the designers chose to make some NPC's that are integral to the storyline invulnerable. Personally, I would have preferred an "all NPC's are killable but when the storyline is broken a warning message appears" technique as was used in Morrowind. Overall, though, it makes little difference unless you are roleplaying a crazed murderer. The game is full of decisions, choices, etc. All of these have consequences - some good and some bad. There will undoubtedly be times throughout the game where you'll wish you hadn't done something, or you thought a choice wouldn't affect anything but it did. I like this in a game, though. It shows that the world actually is affected by the things you do. You actually change the world. It's a good feeling.
The environmental effects are very well done. Rain falling, the glare of the sun, and even an eerie green fog help add more variety and realism to the game.
The leveling system is fairly basic, though well done. When the character levels up, points are received and can be put into any combination of different skills. These skills affect the character's ability to accomplish tasks such as fighting, forging swords, casting spells, or moving silently. It is much the same as many other RPG's out there, so I won't waste much time on it.
As far as the difficulty of the game, I found it to be quite hard. I played Gothic 2 Gold, which has Gothic 2 and the expansion bundled together. The game is really hard. You will die. In fact, you will die a lot. A wrong turn can lead to a sudden death and the loss of time. All I can say about this is to save early and save often. Especially at the earlier levels, the hero is incredibly weak. Insects, wolves, farmers, and just about anything else will kill him. Be careful and stick it out, though, and you'll be in for a great RPG that has a lot to offer.