You will likely want to backup your Outbreak discs to ISO for several reasons:

For backup purposes
Running from DVD is going to be much slower than the majority of players, who will be playing from ISO on their emulators, running from an ISO on PS3, or using the HDD Install method on PS2/emulator
If you are going to apply patches such as the translation patch, you will need to apply them to an ISO.

Ripping the DVDs

Ripping the Outbreak DVDs is straightforward and will produce a single ISO file per game. The Redump Disc Preservation Project put together a simple guide for discs including PS2 discs using free and open source Media Preservation Frontend (MPF).

After you have ripped to ISO, you will want to verify the checksum against the checksum from known good rips to verify that you have ripped an accurate copy of the game. Jay-Jay from PS2-home put together a guide with ways to do this. You can check the MD5 or other has data such as SHA-1/CRC-32 against the values for Biohazard Outbreak and Biohazard Outbreak File 2 at Redump.org.

Ripping Original Discs To ISO

Ripping the DVDs