"Serious obsession" refers to a strong, intense, and often excessive preoccupation or attachment towards something or someone. It implies a level of seriousness and dedication that goes beyond normal interest or fascination. Full definition
You atheists today don't and have a serious obsession to the faith that you grew up in an left or the faith that is most popular in your area. (religion.blogs.cnn.com)
I have a serious obsession with all things breakfast foods and this one is by far one of my favorites. (nymphinthewoods.com)
Can I just tell you that I have a serious OBSESSION with Bumble Bee Tuna... Specifically their Sun - Dried Tomato packed in Olive oil and their Jalapeño packed in Olive Oil! (strengthandsunshine.com)