This takes everything that was good about the original, beefs it up and presents it and a more modern way.
The biggest difference between this and the original game was the graphical updates. Now the player would see rendered images of each potential building and building they bought. More cinematics, etc.
The sound was also improved upon from the first.
So why is this game rated lower than the first? It just was not as revolutionairy as the first. The game progressed nicely here, but it just didnt pack the same punch as the first.
Now there were updated types of zones, buildings, weather, disasters, cars, etc. but the same principals applied. Don't take that as a bad thing.
This game will provide you 100+ hours of fun before you feel like you have even started.
If this was the first simcity released I'd be giving this a 10 or a 9.5 easy.