Duke Nukem Forever was a huge disappointment for a lot of Duke Nukem fans. However, there was a version that impressed everyone back in 2001. That version of Duke Nukem Forever was powered by Unreal Engine and was meant to be a more serious/dark game. And according to Frederik Schreiber, VP at 3DRealms, that version is 90% complete. As Frederik Schreiber claimed, this 2001 version packs 14-16 hours of gameplay and it played partly as an RPG in terms of goals. Players basically had Mission Objectives on their HUD and they could activate them, like quests. Furthermore, you also had an inventory with ID badges, keycards, etc.
In Duke Nukem Forever 2001, players meet and save NPCs, solve puzzles, and try and solve the mystery of what’s going on. Then they meet the infected EDF who’s attacking them and the story evolves from there. Duke Nukem Forever 2001 featured 25-ish levels in single-player and 12 levels in multiplayer (with most of them pretty much done).