It is not piracy As long as you own the game. you can rip it apart and do anything. As long as you don't distribute it.
And, technically a RIP means, chopping something off the disc. Usually.. remove the unnecessary multi5 languages. It will save a GB or so (depending on the title). And, after removing all the unnecessary languages, compressing FMV videos (which are usually in .bik format.) and recording the audio files to much lower size by reducing their bitrate. And match this with some high quality compression techniques. Thats how you get a RIP.
But, there is something called fullRIP. In which the game will be AS IS (except the multi5 language support in some). In this, duty is to first compress the videos and audio to inferior format. And then, restore them to original format while installing using some weirdo algorithms. fullRIPs are very hard to achieve, and that's why there are very few distributors out there.
You can get, make any type of rips as long as you own the game. It is not illegal. But, If you don't... it obviously is.