Ah, I see. THAT is perfectly legal. Downloading game images off the internet is illegal. Be more specific next time. By your first post it sounded like you were a run of the mill pirate.
It really depends on what game you're trying to make an image of. Some are more protected than others, but i've always had success by using Disk Utility. Simply navigate to your applications folder, from there go to the utilities folder, and there you'll find Disk Utility. Insert the CD you want to make an image of. Click on the volume that shows up on the left hand side of disk utility. Then go to the file menu, scroll down to new, then pick the one that says "Disk Image from disk0s1" or something like that. If you can't find that option under the "new" menu button, it's because you don't have the right volume selected. Once you get that part right, it should go right off and make a data copy that you can mount whenever you need it. If you happen to have Toast Titanium, I believe you can make disk images with that as well.
Cheers