Reason #1: Full Immersion
Players like to be drawn into the story. While most PBBG will not take over the entire screen or have heavy 3d graphics, having a background story and a consistent narrative throughout the game goes a long way to having immersing the player in your game. Be forewarned this is one of the toughest of all of the attributes to implement as it takes a methodical, long term, and strategic builder to maintain a good story line.Reason #2: Player Ownership
Allow your players to "own" a piece of the game. Ask yourself what aspects of the game play do you allow your players to control. The most common implementations of this are an in game auction site, allowing players to sell items from a shop, or allowing players to swap items or even create them. One of the best games online that allow player ownership is SecondLife. (Yes, I realize it is not really a game)
Reason #3: Personalization
Do you give your players a way to stand out from other players? The more opportunity you give them to stand out the more invested they become in playing the game. Most games have some sort of built in Avatar system, while this does go toward personalization it has been proven that most gamers have become jaded to the avatar and consider it the same as a personal username. Leaving the Avatar system with a lesser impact than it did in past times.
Reason #4: Rare Items/Actions
Having rare items within your game gives the collector within the gamer something to look forward too. The issue with rare items is that often they are "game changers" in that who ever owns one is semi-god like. In truth a rare item that has less power works just as well as a powerful rare item. There are two caveats to keep in mind, first knowledge of its rarity must be will know, and second the item must have a "unique" appearance within the game. For Example: Everyone knows that finding the "Super Secret Rod of Civility" is really hard to get, and if you get one your face glows red. The only way to get a glowing red face is if you have the secret rod.Reason #5: Showing the Ladder
How easy is it for your players to see their progress in the game? Players like to get that immediate gratification as they rack up the score, so make sure that they can see their name on a scoreboard and see how they progress up it. Even if it does nothing more than point out they they are NOT last on the list (only 2nd to last). This is one that is simple to build but rarely done correctly within PBBGs.Comments are welcome....