For those who were around in 2000-2001 when adult videos started to become popular on TGPs/MGPs/Forums, you'll recall they were mostly 320x240. Even the video focused programs back then were downscaling their PAL/NTSC from 720x576/720x480 captures. Hell there were even 160x120 videos
Back then nobody would even concieve to have 720x480 MPEGs.
Flash forward to today, where to be taken seriously by surfers you must have at least full NTSC/DVD resolution downloadable (see Bangbros, Nastydollars, Deluxepass, Videosz, Videobox etc...) in your members area.
For those saying that Full HD is only for broadcast, bookmark this thread and check back in 1-2 years. History does not repeat itselfs, but it replays fairly close.