By the end of Act 5, Malcolm seems to have earned the kingship of Scotland. Is he more noble and righteous than Macbeth? Is he more like his father...

Malcolm is most definitely more noble and righteous than Macbeth is, and he is much more like his father than Macbeth is as well.  When Macduff comes to the English court to fetch him back to Scotland, Malcolm initially tests Macduff's honesty to make sure Macbeth hasn't sent him to lead Malcolm back like a lamb to the slaughter.  After Macduff has proven his loyalty to Scotland, Malcolm says, "But God above / Deal between thee and me, for even now / I put myself to thy direction and / Unspeak mine own detraction, here abjure / The taints and blames I laid upon myself / For strangers to my nature" (4.3.139-144).  In other words, all the terrible things he's told Macduff about himself are untrue.  He's not greedy at all, is still a virgin, has never lied, and loves the truth.  Macbeth is avaricious and power-hungry; Malcolm is not.  Macbeth is a practiced liar; Malcolm has never lied until this moment.

Moreover, Malcolm says, "What I am truly / Is thine and my poor country's to command" (4.3.150-151).  He longs to serve his country, not to exploit it and tyrannize it as Macbeth has done.  Scotland, he says, will command him and not the reverse.  Macbeth is so power-hungry that he killed to acquire power and killed to keep it; Malcolm has never done such a thing.

Further, after Macduff has killed Macbeth, Malcolm gives a speech to those who were loyal to him.  He says, "We shall not spend a large expense of time / Before we reckon with your several loves / And make us even with you" (5.8.72-74).  In other words, he will reward those who were loyal to him with new titles and lands, just as his father did when he made Macbeth the Thane of Cawdor. 

Malcolm is actually even a little better, a little wiser and more worldly than his father was.  Duncan was deceived in the first Thane of Cawdor and in Macbeth as well.  About the traitorous Thane of Cawdor, he'd said, "There no art / To find the mind's construction in the face" (1.4.13-14).  He laments that one cannot simply tell what another person is thinking based on looking at them.  Malcolm seems to take precautions against being deceived in a way that his father never really did (as he does when he tests Macduff's loyalty, as I referred to above).  This bodes well for his kingship; Duncan was a wonderful king, but it seems as though Malcolm will be even better: he'll reward those who are loyal to him and he's less likely to be deceived by traitors.