How do i migrate software from my G5 power mac to my macbook pro as when using migration assistant it deems the OS X 10.5.8 on my G5 too old for migration, how can i migrate?

Put your data (the Home folder) onto an external USB drive, then restore files from it on the MBP. Do not restore the /Home/Library/ folder in its entirety. All you would need are the Application Support folders for your compatible or upgraded applications and the preference files for those applications.

Many of you applications on your G5 will probably not be compatible with the operating system on the MBP. You can check which are and which are not at http://roaringapps.com/apps?index=a