Being able to go outside of Neocron after a few days in the sewers and just explore and kill anything you wanted (within reason) was such a great concept. The missions from the citycomm felt optional rather than mandatory so no pressure to keep doing them (also having to go to a citycomm everytime makes them very ineffective for xp). It helped so much with the atmosphere and immersion into the game without those "I must do this" pressures.
Even the LE chip for me was a concept that was brilliant, rather than having to choose a PvE or PvP server I could simply take the LE chip out and go do some PvP. Though maybe reconfigure how you can put it back in.
The game did so much right in terms of immersion that other games are scared of trying. I was playing grav the other day and whilst it was decent it gave a step by step tutorial of what to do next. It just felt like I was following a set of instructions of how to play a game. I understand that nostalgia has a part to play in this but there is hard facts to support Neocron letting the player make up his own mind of what to do rather than being spoon fed via tutorials and quests.
It may be a niche market that still wants this but I'm confident theres's still a fair amount of players who prefer this style and enough to make Neocron a success. Now whether its Neocron who takes that market remains to be seen.