i feel religion is important in a marriage. even if a person is an atheist, and i believe that's a way of thinking that can also lead to the truth, there has to be a common ground. mixed marriages must sort out these thoughts.
A lot depends on the thought process and outlook of the couple. I know a person married to someone from a different culture. She goes to Church every Sunday while he performs all his rituals. They don't force each other, they're happy.
Well sure its important. A personality is a collection of needs. A need is based on a collection of beliefs. A personality thus is really based on your core beliefs, as are the choices you are going to make in life. Your compatability with another person is largely predicated on having compatible fundamental belief systems. Everything else flows from there. Without that in place, the best you could hope for is to have fun and some good sex. Not that those this are bad ... but there should be more for a lasting relationship!