Is using DVD decrypter to extract ISO files from a ps2 game disk or just using it in general legal?

Although it shouldn’t be illegal, it is.
Those copyright Nazis getchya every time…

Like, I think that it should be perfectly legal unless you sell the copies because that is gipping the OEMs. If you don’t sell anything and you have copies for personal use, I don’t see a problem but obviously they do…

By law, it is only illegal to distribute copies to others. But some producers may add to their terms of use (a set of rules set up by the owner of an intellectual property or service to govern how their product may be legally used) a clause stating that efforts to break any copy protection they have added to the disk a breach of contract with the purchaser.

In short, if the makers of DVD Decrypter were promoting the use of it in conjunction with games where copy protection is deemed illegal, then the content producers will have had a fair case to proceed in taking action against them.