A little rough around the edges, but a great start to the Gothic series
In my mind, while Gothic 2 is a nice step forward in many regards, I still feel that the story of Gothic 1 is more engaging than its sequel. Undead dragons can't beat the story of the Sleeper, the mysterious creature from another dimension who manipulates people's minds as they sleep. The game's atmosphere is creepy and tense, more so than any other RPG I've played, with the possible exception of Planescape: Torment.
If you've already played Gothic 2 and liked it, it won't be an anticlimax to play Gothic 1. The personality of Gothic 1 is quite different from #2, so it's unlikely you'll get a feeling of deja vu.