YES i've been waiting for a remix of the .hack series! i don't know why everyone thinks the anime music and the game music is the same, because it is VERY different. the anime's music had a large celtic overtone while the game keeps that to a minimum and goes with a more techno approach. 
 
thats the hard part, a lot of the song's don't have names. also, the background music for the "8 phases" and pretty much most the events is exactly that, leitmotifs. but  there are still lots of different background music, ranging from dungeons to killer viruses and hackers on steroids. 
however some of the ones that stood out for me were 
1.the ending for the first 3 of the 4 original games  
link: http://lamda.bluelaguna.net/hackgame/40%20-%20BooHooWoo%20-%20.hack,,GAME%20MUSIC%20Perfect%20Collection%20CD2%20-%20staff1.mp3 
2.(phase 1) skeith: the terror of death's theme  
link: http://cobalt.bluelaguna.net/hackgame/22%20-%20BooHooWoo%20-%20.hack,,GAME%20MUSIC%20Perfect%20Collection%20CD1%20-%20ev05.mp3 
3. balmung and the databug in the cathedral 
link: http://cobalt.bluelaguna.net/hackgame/36%20-%20BooHooWoo%20-%20.hack,,GAME%20MUSIC%20Perfect%20Collection%20CD2%20-%20str9_2.mp3 
4. the theme of cubia(the badass anti-cheat) 
link: http://lamda.bluelaguna.net/hackgame/39%20-%20BooHooWoo%20-%20.hack,,GAME%20MUSIC%20Perfect%20Collection%20CD2%20-%20str01.mp3 
5. the death of mia and the birth of macha (i cried ) 
link: http://cobalt.bluelaguna.net/hackgame/60%20-%20BooHooWoo%20-%20.hack,,GAME%20MUSIC%20Perfect%20Collection%20CD2%20-%20str19.mp3 
6. drain heart(the death of aura and morganna and the birth of the perfect AI aura) OR "the system decides to finally **** everyone over including itself and then fixes itself in the process" 
link: http://lamda.bluelaguna.net/hackgame/63%20-%20BooHooWoo%20-%20.hack,,GAME%20MUSIC%20Perfect%20Collection%20CD2%20-%20str21.mp3 
here is a video of drain heart 
http://www.youtube.com/watch?v=8eb-8vmxU-s 
yes the ending was cliche but i still daaaawwwww'd  
 
also the complete soundtracks for .hack//game (the first 4 games) and .hack//g.u. are available here 
http://bluelaguna.net/splash/dothack.php