Let's take a look, courtesy of a report from online piracy specialists TorrentFreak!
Having examined "(nearly) all torrents that can be downloaded from public torrent sites today", they've been able to obtain a list of the most popular gaming platforms among online pirates.
Unsurprisingly, given its age and the ease with which games can be pirated, the PC is at the top, and at the top by a very wide margin. After it, though, come the two platforms most concerned with piracy this hardware generation, the PSP and Wii. Things get a little murkier after that, TF unable to break down the numbers between PS1, PS2 and PS3 (presumably most are PS2, given the difficulty in cracking a PS3) torrents or Xbox and Xbox 360 torrents.
To see the complete list of figures, check out the chart below.
Interestingly, the same study showed that games only make up 3.3% of the total number of torrented files on the internet, paling in quantity next to movies, TV shows and music.
A Snapshot of the Public BitTorrent Landscape [TorrentFreak]