You could go with a 'realstic' approach. THat article gives you plenty of ideas to use to make a non-generic RPG.

There is plenty to do:

Have an actual plot- many RPGs just thrust you into saving the world against some generic nefarious threat. There is very little character development, just lots of combat. However, as the name implies a ROLE PLAYING game should involve playing a role, not just number crunching (in which case it should be stat game). FOr a single player game, I suggest looking at games like Plansehift: Torment and the Baldur's Gate games to see some interesting plots and NPC development.

Try a different setting- How many times must Tolkien be copied? Try something innovative. Even TSR (the original Tolkien ripoff company who published D&D) did. Take a look at the Dark Sun setting (a sun drenched, post apocalyptic world blasted by magic where survivors try to eke out an existence), Planescape (multiplanar beings in an eternal struggle for influence), or even Al'Qadim (Arabic fantasy). There are a ton of historical settings rip for RP potential such as ancient cultures like the Egyptians or Romans, pre-Columbian South American peoples, ancient Chinese, Samurai Japan, colonial Europe, etc. Or even try the future!

Give players meaningful options. Most RPGs seem to be combat centric. But what if players want to socialize and try to influence NPCs through reputation, threats, bribes, or seduction? What if a player would be perfectly content baking bread? Why must all magic aim towards combat? Why not enhancing other abilities or adding new options? Even in combat, players should have choices. Don't make certain weapons or armor better, make them different. So maybe leather doesn't protect much, but its light and easy to repair or replace. Perhaps chain mail protects more but the added weight fatigues the wearer quickly and the links are more costly to maintain. Continuing this trend, perhaps plated armor protects most of all, but is very bulky, hard to utilize effectively without training and very expensive to maintain. Remember, this may not be entirely realistic, but balance > realism. (In real life, plate was quite flexible, not terribly heavy, had better weight distribution than non-foundation IE chain armor. But it was also only availible late in the medieval period, needed very skilled workers to fabricate, and was far beyond the means of all but the wealthiest in a society where social and economic mobility was practically impossible.)

Danial.Beta wrote:

The biggest thing to remember, never let them finish. Although giving them a nearly impossible task to complete is a good idea in an online RPG, letting them get to a point where the are "done" means that they have no reason to play any more. I guess this idea does conflict with any story line you might put in place, but if done well, it could still work out.

The Haven Seed way of accomplishing this is by including a genetic system and a natural death system. I will allow people to circumvent natural death, at great risk, but otherwise age is a ticking time bomb that limits achievement and makes the idea of marrying and settling down after 20 years of adventuring a good idea. The player's old warrior might become a hunter in his later years and raise a son. The player trains the son as a warrior. When the warrior dies, the player assumes the role of his son and continues play as a new character.

I'll have to try it out on the community at large, however... I can envision some possible proponents and more than a few possible detractors. =)