As one of the year's most talked-about and highly-regarded games, it should come as no surprise that BioShock Infinite is still selling incredibly well.

According to Joystiq, Irrational and Take-Two Interactive believe BioShock Infinite can be the most successful entry in the franchise. The sequel has now sold more than four million copies since launching this past March.

"BioShock Infinite is North America's best-selling multiplatform release so far this year, according to NPD," CEO of Take-Two Strauss Zelnick said during an investor's call. "The title has crossed the 4 million units selling mark, and we expect it to become the top-selling release in the BioShock franchise."

With new downloadable content out this week, and more on the way, fans should be able to enjoy BioShock Infinite for months to come. Just how well it will sell for the remainder of the year remains to be seen, but it definitely sounds like Take-Two is very happy with the results thus far.