When Hamlet speaks with the captain about young Fortinbras, on his way to fight for some scrawny piece of land that has no real merit, he cannot help compare himself to the young Norwegian. Fortinbras is busy working to restore his own and his father's honor, while Hamlet remains relatively inactive and has not yet achieved any real measure of revenge on his uncle. He says,
Rightly to be greatIs not to stir without great argument,But greatly to find quarrel in a strawWhen honor’s at the stake. How stand I then,That have a father killed, a mother stained,Excitements of my reason and my blood,And let all sleep—while, to my shame, I seeThe imminent death of twenty thousand men,That for a fantasy and trick of fameGo to their graves like beds, fight for a plotWhereon the numbers cannot try the cause,Which is not tomb enough and continentTo hide the slain? Oh, from this time forth,My thoughts be bloody, or be nothing worth! (4.4.53-66)
But I am very sorry, good Horatio,That to Laertes I forgot myself,For by the image of my cause I seeThe portraiture of his. I’ll court his favors.But sure the bravery of his grief did put meInto a towering passion. (5.2.80-85)
If you consider the characters of Hamlet, Laertes, and Fortinbras they have remarkable similarities, thus inviting comparison. First, they are all sons of murdered fathers. Hamlet's father, like Fortinbras's, was a king and military leader. Both were killed by men wanting power. Interestingly, Hamlet and Fortinbras were both denied the throne after their fathers' murders. Uncle Claudius kept Hamlet from the throne of Denmark, while Fortinbras's uncle usurped his throne.
Considering Laertes, he is remarkably similar, as well. Both Hamlet and Laertes have murdered fathers, though Polonius isn't a king. Laertes and Hamlet are both tragically affected by Claudius. Both Laertes and Hamlet are killed by the poison rapier that Claudius chose as a lethal weapon. They were both killed in the pursuit of revenge, which Hamlet's V.ii apology to Laertes proves could have been avoided.
Laertes and Fortinbras both experience something similar to Hamlet, in that they are driven to seek revenge. Unlike Hamlet, they actually act on their feelings and do not suffer from the paralyzing doubt that Hamlet feels.