Almost as good as its predecessor
The characters for instance are less fleshed out in M2. Vito the main character is less engaged in moral dilemma's than Tommy in the original was and the story doesn't develop the character in the same way it did in the original. Tommy started out as a cabdriver and stumbled his way in the criminal world of Lost Heavens mafia. Vito on the other hand decides early on in the game he doesn't want to live as his father did (worked himself to death) and that's about all the moral motivation for his actions. He is much more the one dimensional all American tough guy fighting his way through cruel and hard times.
Another thing the story of M2 did worse in comparison is the way friends and allies turn against each other. In the original story these were the pivotal moments of the story that got you moved like in a good movie. M2 didn't had those same moments mostly because Vito is too one dimensional for experiencing treason and betrayal like Tommy could. I couldn't really get under Vito's skin. Most of the things he does, he does because he just is a tough guy.
M2 did do a lot of things equally good as its predecessor. The music again worked brilliantly as a submersion device. Driving around in perfect historically correct recreated cars is just in itself a treat. They kept this feature in the game (Vito has to drive a lot from one place to the other) despite the complaints general shooter fans had about the driving part of mafia. This means they hold on to the idea not to make a standard shooter but a game that wants to be much more than that.
And for the second time I think they succeeded in doing that.
I had such a good time spending time in this world of M2 I felt the ending really came to soon. They could have made you more engage with the city and exploit the collection and reselling of cars for instance. A lot of idea's come to my mind that could have been more fully worked out.
All in all it's a welcome different gaming approach from the blizzards, EA's and activision type of games. I just wish I don't have to wait another eight years for a sequel.