It’s been just under one year since social-gaming startup Playdom launched Mobsters, which has grown to become the #1 game on MySpace with 13.5 million total installs. Now, the company is taking the incredibly popular game mobile with its first iPhone App, dubbed Mobsters: Big Apple (iTunes Link). And while it may not be the first such mafia-related game on the iPhone, it still has a few tricks up its sleeve that could turn it into a major hit.

Now, Playdom isn’t close to being the first mover here — we covered iMob back in January, and we’ve seen competing social gaming companies like Zynga and SGN launch similar games based on the Mafias, Vampires, and a number of other themes. But Playdom has one advantage that the others don’t: it has directly hooked Mobsters Big Apple into its counterpart Mobsters game on MySpace, which means millions of players will be able to begin playing with the account that they’ve spent the last year building up on the social network. SGN and Zynga both offer Facebook and MySpace games with similar themes to their iPhone games, but for whatever reason they haven’t linked them together, which means gamers have to begin anew if they start playing on the iPhone.

Aside from a large existing user base, Playdom also has the benefit of being able to use much of the same content from its well-established MySpace game on the iPhone, which means the new mobile app has access to 65 missions and plenty of items. And because both games use the same backend, the company can continuously add new content to both games. The iPhone app can’t currently connect to Playdom’s Facebook game, but the company says support is coming.

As with other games in this genre, gameplay largely revolves around completing missions and becoming more powerful by acquiring better weapons (there’s also a time constraint that forces you to keep coming back for more). It may not sound particularly appealing until you’ve tried it out for yourself, but once you do it’s easy to quickly become totally addicted. Playdom has done a good job enhancing the experience with audio clips (you’ll hear things like “Magnifico..” when you complete a mission), and assorted art assets.

Now we’ll just have to wait and see if Zynga and SGN strike back with their own web-connected updates, or if there’s a reason why they made the decision to hold off on adding that functionality.