All hobby games (not video/computer games) go viral, go hardcore, or vanish.
Viral – Enough people play that the game becomes a staple of play in gaming settings. Examples include: Dungeons & Dragons, Magic, Pokemon, Settlers of Catan, Risk, Monopoly, HeroClix. Board games don’t tend to go viral with the same energy as collectible games, but I do believe the all the top selling board-games owe their success largely to a viral-type effect. Nowadays many games are designed from the outset to go viral, and if they don't their failure is assured. Games from big publishers that are canceled quickly almost always fall into this category.
Hardcore – Relatively small fan-base, but large enough to sustain the game provided their needs are met. Precarious situation because new fans are hard to attain and the existing fans are hard to keep. Nearly all games (all things, really) have a hardcore following to some degree. Hardcore games are often discussed online far more than they are played (because they never went viral, opponents are hard to find.) When games are designed to be hardcore games, they can be very successful whether or not they go viral. It is more difficult for a publisher to support a game designed to go viral but instead gained a hardcore audience. Hardcore friendly games are easier to create because almost anything can achieve some level of hardcore following. The only question, is the following big enough and spendy enough to support the game? Spendy fans are often important to the Hardcore game. The more you charge, the less you have to sell to make a profit and the smaller your Hardcore audience has to be in order for the game to succeed.
Vanish – Cease to be published. In some cases a game is meant to be a limited run, so vanishing isn’t always a failure. Usually the goals of the publisher haven’t been met and it’s obvious they never will be.
Many games aren’t designed from the outset to ‘go viral’ or ‘go hardcore’, but in hindsight it’s usually easy to see why games had the success or failure they had. TCGs are largely dependent on going viral for success, and tend to be designed with that purpose in mind. Most RPGs, on the other hand, are designed for hardcore success only.
On the other hand, making something go viral is relatively hard to so (despite what the viral marketing books tell you!)-Adam!!!