Windows: Use DVD Decrypter
There are other more recent updated programs however (Such as Imgburn), this is the only one I can find that doesn't ask you to install toolbars and other malware.
Step 1: Put your PS1 or PS2 disc into your computer.
Step 2: Open DVD Decrypter
Step 3: Click Mode>ISO>Read
Step 4: Choose the destination of the file, by clicking the little folder+magnifying glass button.
Step 5: Click the DVD button at the bottom.
Step 6: Wait for it to finish burning.
Step 7: Play ISO in whatever emulator you use ( PCSX-Reloaded is recommended)
You'll need homebrew installed, so if you don't have Homebrew already, go here check which Homebrew installation method works for what System Version you have ETC. Now that you have Homebrew Channel and Cleanrip installed here are instructions.
Instructions (Make sure a gamecube controller is plugged into your wii)
Step 1: Insert your WII or Gamecube disc and your SDcard or USBstick into the wii.
Step 2: Choose what device you're using, USB or SD using the Gamecube buttons
Step 3: Choose which file format your SD or USBstick is. (Must be FAT32 or NTFS, if not you'll need to format it, read down below for instructions)
Step 4: If it asks you download Redump.org bat files. Press no.
Step 5: Press A on your Gamecube controller and it will start the ripping process, wait for it to finish and when its done the ISO file will be on your SDcard or USBstick.
Instructions for formatting SDcard/USBstick
If your SDcard or USBstick is not FAT32 or NTFS heres how to format.
Step 1: Plug your SDcard or USBstick into your computer. Step 2: Click on Start Menu, click on computer. Step 3: Rightclick on your SDcard Or USBcard. Step 4: Press Format, and choose FAT32 or NTFS (Make sure you backup files if theres any on there, as the formatting process will delete everything)
Required Hardware: Broadband adapter, CD-R Drive