One of the hallmarks of Shakespeare's many plays is the way that in them he is able to tap into universal themes, that are just as relevant in today's world as they were in his own times. Also, what is notable is the way that his plays can be performed in a number of different cultures and geographical locations and still be just as relevant. I remember reading about a production of this play that was set in an African tribe which lost nothing of its force or power in the way that it had been adapted to fit this setting.
The central theme of this brilliant tragedy is that of ambition and how pursuing it can corrupt us as humans and make us become evil. Macbeth is taunted by the possibilities of the power he could achieve and the kind of glory he could attain, which corresponds with his own ambition and his desire for power. Note what he says in his famous soliloquy in Act I scene 7:
I have no spur
To prick the sides of my intent, but only
Vaulting ambition, which o'erleaps itself
And falls on th'other--
The dangers of ambition and how it can lead us to jump so high that we metaphorically fall on the other side of the horse we are trying to mount is a message that is just as relevant for today's world as it was then, as it corresponds to being human and the dangers of letting ambition drive us so strongly that we end up doing things that we either regret doing later on or that we end up failing. This play therefore, is just as relevant because of its themes today as it was then.