Just in time for E3, Nielsen Mobile has released its latest stats on the US mobile games market, claiming that there were 19 million game downloaders in the first quarter of this year.

It's also estimated the top five mobile games by revenue share. In order, they are: Tetris, Bejeweled, Are You Smarter Than a 5th Grader?, Guitar Hero III Mobile, and Pac-Man.

Puzzle/Strategy is the most popular game category by revenue share, followed by Action/Adventure then Sports/Racing.

Nielsen has also been digging into Guitar Hero III Mobile's performance, claiming sales have increased each month since December, hinting at a word-of-mouth viral effect.

However, Nielsen also estimates that the game currently accounts for more than half of Hands-On Mobile's publisher revenues. If true, this may be a concern for the company in the long-term.

With Guitar Hero's console publisher Activision having just merged with Vivendi, it would be logical to assume that whenever Hands-On's licence runs out, Activision will take it back in-house for Vivendi Games Mobile to handle.

Still, Nielsen's stats also shed some light on who's playing Guitar Hero III Mobile. Apparently, 75 per cent of purchasers were under 25, while 54 per cent were 13-17 years old, despite this age group representing just 11 per cent of overall mobile game purchasers.

It also shows a pretty even gender split, with 47 per cent of purchasers being male and 53 per cent female.