Gothic is a great game and is part of a series that I believe is better than the Elder Scrolls series.
Gothic is a game that shares some general aspects that you'll find in a game such as Morrowind or Oblivion. Gothic is a very open ended RPG that throws you into a large landscape you are free to explore as you choose and which gives you a good handful of quests and options that you can solve when you feel ready.
The graphics in G1 are definitely well behind those of Morrowind but are still quite acceptable. The fact that the game implements long range rendering makes a big difference in giving you a true feeling of being part of the world. In Morrowind, nothing was rendered beyond a given rendering distance, but in G1, far away mountains and geographic features are still rendered, but with less detail.
While G1 and G2 appear to be based on the same graphics engine, I would have to say the visual presentation in G2 is significantly better. The textures and details to the environment are done much better. Also, the plants and trees in G2 are far superior (even to Morrowind) and they provide for a very lush and rich environment. G1 still has the sense of walking through areas with trees and plants dotting the region, but not a true wilderness packed with flora.
G1 is not packed with side quests as you'll find in Morrowind but there is still a handful of quests to undertake and there are a number of different paths you can take in proceeding along the main quests. At some point in the game, you have to join one of three camps, each having a different effect on how the game progresses.
There is no monster leveling as there is in a game such as Oblivion which means that the game starts off very hard. After a short time, you gain a minimum level of combat effectiveness but there are still monsters and regions in the game that you can't fight through until much later as you'll get killed in a heart beat.
Many people have commented on the control system in G1 and even after playing G2, I found the controls in G1 to be quite cumbersome. For the first hour of the game, I was extremely frustrated because I felt as if my weapon was more or less unresponsive to my commands. Once I got some armor and a decent weapon, I was more able to survive. The controls are definitely tolerable but are rather bizarre.
The inventory system is one of the worst systems ever implemented. To move items in your inventory you have to press the mouse button (or control) along with a movement key, a rotate key or a shift-movement key to move items in units of 10, one or 100. To complete a transaction with a merchant, you have to figure out that you have to press the enter key. To pick up an item, you have to press mouse-forward and to drop an item, you have to press mouse-back. Even by the end of the game, I would occasionally get the keys wrong.
The difficulty of G1 is just about right. I found G2 to be much more difficult in terms of the monsters you have to fight. G2 is a game that is mostly about killing one monsters at a time, but in G1 it doesn't take too long before you can take on groups of monsters without having to rest or recharge. The magic system in G1 is always much more enjoyable. In G2, the cost of magic spells relative to the amount of mana you have was simply too high. In G2, you will find yourself casting a few spells only to have to rest to get your mana back. In G1, you can cast a lot more of your spells before having to recharge your mana. This makes playing as a mage much better.