In my edition of Shakespeare's Hamlet, the line numbers you give feature Hamlet speaking before he dies. In my edition, I think the lines you ask about are 380-388, in which Fortinbras says:
...Let four captains
Bear Hamlet like a soldier to the stage,
For he was likely, had he been put on,
To have proved most royal,...
Essentially, all Fortinbras says is that if Hamlet had been crowned king, he likely would have proved "most royal."
What being royal consists of is probably a matter of opinion, but in general, Hamlet, throughout the play, is noble, is fully aware of the fact that actions have consequences, shows leadership abilities, apparently is an excellent swordsman, and is a good man, at least for the most part and when it comes to the larger issues of a kingdom. These traits suggest Fortinbras is correct, and Hamlet would have been most royal.
Concerning what happens in Denmark with Fortinbras in control, any answer I give would be purely specuation and irrelevant to the play. Finally, Fortinbras doesn't really have any revenge to get, since King Hamlet, the leader of the forces in the battle during which King Norway was killed, died long ago.