Yes there is a way. This is how i do it:

I have a class PageOrder (and also for blocks a class BlockOrder)

public class PageOrder
{
    public const int Home = 1;
    public const int SomePage = 10;
    public const int SomeOtherPage = 20;
    public const int AndSoForth = 30;
}

Then i annotate my PageType with the following (HomePage as example),

[ContentType(
    DisplayName = "Home",
    GUID = "someGuid", 
    Description = "someDescription",
    AvailableInEditMode = true,
    GroupName = ContentGroupNames.General,
    Order = PageOrder.Home)]
[ImageUrl("~/someFolder/Home.png")]
public class HomePage : PageData
{
}

You can see the line Order = PageOrder.Home . This is the magic.    

It's very handy to have the class PageOrder since you can quickly see all the pages you have and the sorting they have between them. (instead of having to look at each individual pagetype class)

I'm, however, not certain how the Order is taken into account together with GroupName, but it seems groups are ordered somehow by the PageOrder attribute.

Good luck and greetings, Martijn