Alongside a breakdown of per platform online gaming popularity, the company noted that "an average of 20 percent of all games purchased by online gamers were digitally downloaded - up from 19 percent in the 2009 study and 18 percent in the 2008 study."

Overall, the popularity of online gaming dipped across the past year (54% of those surveyed said they played games online, down from 56% in 2009) but those that did play online played more, reporting an weekly average of 8 hours, up from 2009's 7.3 hours.

As for the breakdown between PC, Xbox 360, PlayStation 3 and Wii:

The PC is still the most-used system for online gaming, with 85% of online gamers reporting using a PC for online gaming activities. Among non-PC systems, the Xbox 360 maintains its leadership for the third year in a row as the top video game system used for online gaming at 48%. In contrast to 2009, when Wii was leading over PS3 by 8 percentage points, PS3 and Wii are now neck and neck, with about 30 percent of online gamers reporting that they use each system for online gaming. This is due to an increase in use for online gaming on the part of the PS3, which increased 10 percentage points since last year. The top three systems with the highest average hrs/wk spent gaming online (using the respective systems they own) are: Xbox 360 (7.3 hrs), PC (6.6 hrs) and PS3 (5.8 hrs).

And, as usual, a look at the methodology:

Methodology
Data was collected via online survey. Fieldwork was conducted from January 4 - 19, 2010. The survey was completed by 18,872 NPD Consumer Panel members ages 2+. Respondents age 2-12 were captured via surrogate reporting. Final survey data was weighted and balanced to represent the U.S. population of individuals ages 2+. In order to qualify for the survey, respondents had to report that they personally use at least one system or device for gaming. In order to qualify as an online gamer, respondents had to use at least one system or device for online gaming. Both online gamers and gamers overall (whether online or offline) were included in the study.