<apex:commandLink value="{!user.Name}" action="{!userDetail}">
    <apex:paramname="userId"value="{!user.Id}"/>
</apex:commandLink>

public PageReference userDetail() {
    String userId = ApexPages.currentPage().getParameters().get('userId');
    PageReference pageRef = new PageReference('/'+userId);
    return pageRef;
}

HYPERLINK(Id)