There are already distinct ways in which pop-culture is similar to religion. For my example I'll discuss Star Trek, which doesn't need much of an introduction.
It's safe to say that there are all types of Star Trek fans, each with their own beliefs and personalities, but they are all united by their shared fandom and the rituals that go with it. This could be anywhere from attending comic-con to watching a full marathon in one sitting, it depends on the extent they want to take it to. Some people may actually follow Kirk as a role-model and hero, while others could simply see him as a grand character in a story.
We see this more and more with organized religion, people adhere to the religion to whatever extent they wish, and their adherence is on a continuum. Religion has become a lot more relaxed over the course of the 20th century, allowing for people to make what they want of it, similar to Star Trek. For example, while the beliefs of all Christian's might not line-up exactly, they are all united by the ritual of Sunday Mass, or reading the bible, or even studying it for those who give it a larger role in their life.
Bottom line: While religion/Pop-culture doesn't necessarily have to define who people are, it does show what they adhere to, and through those various levels of adherence it can play a larger/smaller role in an individual's life. But at their base, they both serve as a means to unify people into one collective and feel a part of something larger, which alone can provide them with a sense of meaning or purpose.