I only just saw this noted in this months issue of Toy & Hobby Retailer magazine, but apparently it was official since September.
Thanks to the Lego Movie this year, and a 21% drop in Barbie sales, Lego overtook Mattel in terms of revenue for the first half of this year.
For the first six months of 2014, Mattel earned US$2 Billion globally, while Lego earned US$2.03 Billion globally.

I think Hasbro should be third, but their last quarterly report said that they earned US$1.47 Billion (which would make it a lot more than US$2 Billion for six months), and the revenue each year for the last five years has been over US$4 Billion, which also makes it over the US$2 Billion mark.

Anyway, at the moment it looks like the three are close to each other, with Lego being officially number one for the last six months.
Meanwhile Tomy is closing in... giving us two American, one Japanese and one Danish company fighting over the top toy spot.