Like all too many other people, I found the ending of ME3 to be unsatisfying and badly written, and like no small number of other people, I felt compelled to rewrite it so that, in my own canon, this is how it really ended. But in case you don't yet know how it ends and want to stay that way, I've cut the post to allow you to do so.
( Here Be Spoilers! )
( Here Be Spoilers! )