Gay marriage should be a non-issue. Government has no business being in the marriage business; remember separation of church and state? In this instance, all government should be involved in is domestic partnership contracts, and all who desire a formalized contractual relationship with another would have to meet legal contractual requirements: basically that each party to the contract has the legal capacity to sign a contract - meet minimum age and mental capacity standards. Of course, individuals may live together without a contract, have children and raise them, and purchase property, and it seems today that such arrangements are more common than marriage or contractual alternatives.
As far as marriage itself, it is a religious act. If any couple can find a church that will marry them, may their gods go with them.