I love Gothic 1/2/3, all of then are masterpieces IMO but each gothic has his problems.
G1 - Is too short. According to how long to beat, only Arcania(15 hours) and forsaken gods(17 hours) are shorter than G1(22 hours), source :
https://howlongtobeat.com/#search1
G2 - I din't liked the mage gameplay; Looks like the devs assumed that you ended G1 as a warrior and the mage gameplay isn't exactly good. I say that because Xardas who teaches you circle 6? He can't teach circle 1 and take you as a apprentice now. Why Milten can't give a testimony that you was a fire magician apprentice of Corristo who helped a lot on old camp and be accepted as a fire mage? Why you can't make peace with water mages by proving then that you did the right thing on G1? Why you can only be on ring of water, not in circle of water? Being accepted into the circle of fire requires a lot of boring quests. Sheep escorting, then put a novice to sleep to steal a weapon and use against a golem(completely against what a Lawful good servant of Innos should do. A novice who steals should be expelled, not promoted) and finally when you can be a fire magician, you can cast TWO fire arrows and ran out of mana...
On my mage run, i was using mostly Summon skeleton Goblin or Ice block and spamming melee attacks. Damaging spells are trash. On G1, most spells had 20~50 damage per mana Cost. On G2, most spells had a 6 damage/mana ratio... A mage who invested 95 LP on the first game to have 100 mana, could throw 10 Storm of Fires totalizing 5000 damage in area of effect. On NotR, the same 95 LP starting with 10 mana and investing 20 to reach 30, then 60 points to reach 60 will have only 15 LP left, enougth to have 65 mana. 65 Mana could only throw 3 Small fire Storms and not even a single charged Large Fire Storm. To kill a Orc Warrior, i need at least 4 Small Storms.
G3 - Is unfinished. Is barely playable without the community path and at least consequences mod.
But G3 is my favorite by a simple reason.
Water Magic early on. You can only become a water mage on Gothic 1 at chapter 4. On Gothic 2, you can't become a water mage at all. But on G3, you can after leveling few levels and inesting into ancient knowledge, find a druid and start to learn water magic early on. And water mage spells are cooler than ever. HAilstorm, summon golem(on g1 was a scroll only spell), tame even shadowbeasts, put guys into sleep, ice explosion...