Huge city, lots of races and cop chases, cool cars with infinite customization options, great soundtrack ... fun!
Get a powerful car, be aware of your surroundings, use the environment to your advantage and you'll have no problems winning. Compared to games such as Race Pro, vehicles in Midnight Club are very easy to drive, but nevertheless I prefer its driving mechanics to those in the Need for Speed series.
There are plenty of cars for my taste, but some people complain that there are not enough, luckily you can get a DLC that will add more cars. The customization options are really insane. You can customize the exterior (body parts, paint, logos, exhausts, lights, neons, rims, tire dimensions etc.) and the interior as well (gauges, seats, steering wheel and so forth). The list goes on and on. Basically you can customize pretty much everything =)
There's plenty to do in the city, there's lots of races and events. The city also feels quite alive, the traffic is much more "intelligent" when compared to NFS. Cop chases are cool too, but so far I never had much problems getting away from them.
The soundtrack is awesome and varied. There's rock, hard rock, hip-hop, rap, electronica, techno ...
I haven't really checked out any of the online modes, because there's still so much to do in single player. Basically what I like most about this game is that you can get a car that you like, customize it so that it looks exactly how you want it and then you go and participate in fast-paced races that are accompanied by comments from people that are sort of 'polite gangsta wannabes' =) It's like playing GTA where people say the exact same thing but in a more civilized way. I find it quite funny ... and refreshing at times =)