1. Gothic II.
2. Gothic I.
It doesn't really matter what comes next.
After that, the games I like the least start, and the rest are just "others." Well, I could also add Heroes of Might and Magic V, because I play it quite a lot, and I enjoy it.
I just finished "Period of Decay" (for the first time), and the first and second games; now I'm going to play the episodes. The second one is a great game, very diverse, and I enjoyed it. But I wouldn't call it my favorite.
I'm curious about what the episodes will be like. I think the developers have already explored everything in the second game, so it will be difficult to come up with something new.
Added 2 minutes later
1. Gothic II Addon
2. Gothic
3. The Elder Scrolls IV: Oblivion
4. Heroes of Might and Magic V: Tribes of the East
5. Heroes of Might and Magic III: Shadow of Death
Almost everything remained the same, except that Oblivion has moved much lower, maybe it will be replaced by Risen (well, I'll play it first, I'm playing it now - I like it, but they say the first one and a half chapters out of six are not boring).
And the first two Gothic games can be swapped in places.
Although I don't know, I can't decide. Better like this: 1-2. Gothic & Gothic II + Addon