Questions about backing up ps2 games

[Shannick]

I have tried to back up some ps2 games. Sometimes they work and sometimes they don't. I am trying to back up one called Champions of Norrath. I make an image but when I try to burn it back it says it is too big to fit on the disk. I checked the size and it shows it is small enough to fit on a standard dvd blank> Do some of the games have something in them that makes them show to be to large to fit back on a blank. I know I am vague about this but I am new.. Any help would be appreciated.