So far, it looks like the Samsung Galaxy S III is poised to surpass every record set by its predecessors. According to JK Shin, head of Samsung's mobile division, Samsung will likely sell over 10 Million units of the Samsung Galaxy S III by July. In fact, supply constraints on parts has made it difficult to keep up with world-wide demand of the new phone, but Samsung is working hard to improve things. Here's a quote with some details,

"We're getting far better reviews on S III than we did with its predecessors globally ... and supply simply can't meet soaring demand. We've sent executives and staff to almost all our (component) suppliers to ensure a smooth offering and hopefully things will get better from next week," Shin said.
Samsung has done a magnificent job in positioning themselves to become a global leader in the smartphone industry, and the Galaxy S III is a prime example of how they are pushing technology to new levels.

Source: S3Forums via AndroidAuthority