In SharePoint 2010, is there any chance to create a parent content type? If so, how? I want to create a new parent content type and inherit it for other types.
In SharePoint, all content types inherit from "Item". You can create any number of new Content Types, that inherit any number of times from each other (singularly, no multiple inheritance here), but they must ultimately inherit from Item. There is no getting around this.
Also note that it's impossible to change the parent content type for an existing content type. You must create re-create a content type and inherit from the desired one if you wish to 'change' the parent content type. Unfortunately for child content types, this also means re-creating them.
Take great care when choosing your content type hierarchy, and devote significant effort (read: time) in this area of your information architecture design, as it is very difficult, if impossible to change later in use.