Emotions evolved a long time ago and pain and pleasure are even older. They are essencial for survival of organisms and the intensity is apropriate for their function. It is therefore reasonable to think other organisms feel them with similar intensity. If anything, they need to rely on them more, so the experience could be more intense for them. There’s surely going to be quite a bit of diversity though.

Edit: Let me add that this is an awsome question. Thanks for making me think about the way other people, animals and different organisms experience the world. I love it!