WTH are you talking about?
First of all 360 ONLY supports DVD dual layered.. or DVD9.. FOR GAMES!..
The HD-DVD player (179 extra) is ONLY for MOVIES! (so 9 gigs for games, and 30 gigs for movies)
Second of all.. yes the PS3 only supports upto 50 gigs not more than that.. Because it only supports dual layer.. (supports 50 gigs for both games, and movies)
And LASTLY, yes the PS2, and wii only supports single layered dvds which are 5 gigs..
Review/Support for games (not movies):
360 supports single/double layered DVDs. (5/9 gigs)
PS2/Wii only supports single layered dvds. (5 gigs)
PS3 supports single/double layered Blu-ray.. (25/50 gigs)
Hopefully that was clear enough.. and your question is answered.
PS Gamers Network - My new website, please contribute. Includes Wii and 360 Forums as well. http://z15.invisionfree.com/PS_Gamers_Network