SimCity 4 is arguably one of, if not the best city builder games out there. It is unmatched in quite a few ways.
In terms of graphics,, it's timeless. i'm amazed how well the visuals have held up over the years. I think the realism mixed with a distinct art-style is what does it. The not quite isometric camera angle and 3D assets go a long way as well.
Game-play and simulation is what really make SimCity 4 stand out though. You're not just zoning a bunch of RCI and watching all the money roll in. You actually have to be careful and manage your funds or else things will go south quickly. Yet at the same time, it's extremely rewarding to see your city succeed.
You're also provided with a plethora of ways to keep track of what's going on in your city. Not only do you have advisors and graphs; but you also can also turn on a bunch of different overlays to look for pollution, traffic, crime, etc. One of my favourite features though is the query tool. With this you can check how and where residents commute on top of other things.
With Residential and Commercial; not only can you choose 3 different density levels, but you can quite easily control the wealth too. There's also 4 different types of industrial (Farms, Dirty, Manufacturing, and High-Tech) with 2 density levels for all except farms.
I could go on and on about how great this SimCity 4 is but there's just so much. That's not to say it doesn't have flaws though. Vanilla traffic path finding is pretty bad, there are some game breaking bugs, and it just does not like modern computers very much. Fortunately most of this can be fixed with mods and some tinkering.
In the end i'd highly recommend this SimCity 4 to anyone who enjoys city building games.