Samsung has a good reason to celebrate as it has sold more smartphones than Apple in the U.S. in May. This is the first time that Samsung has outsold Apple in smartphone sales in the U.S. since the launch of the iPhone 5 last September.

The Samsung Galaxy S4 can be credited with helping Samsung achieve this goal as it was the top selling smartphone at T-Mobile, Sprint, and Verizon, it was also the second best selling smartphone at AT&T right behind the iPhone 5 in May.

U.S., Canaccord Genuity analyst Michael Walkley attributes the success due to strong sales of the Galaxy S4 combined with better than expected sales of both the Galaxy S3 and the Galaxy Note 2. The Galaxy S3 and Galaxy Note 2 have seen increased sales since almost all carriers in the U.S. are offering the Galaxy S3 at deep discounted prices, some even offering the smartphone for free when signing a new two-year contract. Sales of the Galaxy Note 2 have also picked up as its price was lowered as carriers look to rid inventory before the Galaxy Note 3 becomes available. The phablet is expected to be announced in September and see a release shortly thereafter.

Samsung is believed to have spent close to $2.5 billion on marketing and advertising in the first quarter of 2013, which catapulted sales of Galaxy smartphones. "Samsung's marketing is the reason it's selling more phones than anyone else," says Walkley: "We believe dominant sales of the S4 versus other Android smartphones was driven by Samsung's extremely strong Galaxy consumer brand and well-executed marketing campaign, as our surveys indicated store representatives often recommended the HTC One ahead of the Galaxy S4."

The report also points out that Samsung, like Apple, sees a strong increase in sales of any of its new smartphones, proving that the Galaxy brand is on par with iPhone when it comes to consumers choosing a new smartphone. Samsung has stepped up its advertising in recent years to educate consumers on why it believes its smartphones offer more advanced features than Apple's iPhone. The plan has cost Samsung billions of dollars in advertising per year but the plan has paid off and it has turned into a two way race between Apple and Samsung in the smartphone wars, while its rivals continue to batter for the very distant third spot in overall smartphone shipments.