I used to like simcity 4 a lot.. A LOT.
The new cities xl2011 is nice, but different than simcity at the same time. Personally I like it.
It all depend on what do you like about simcity.
IMO, cities XL got the transit system much more realistically made than simcity, also the utility building (like police, hospital etc) instead of a circular radious, in cities xl it all depends on the road you put it. Like, the radious depends on how much the ambulance would need to travel to reach a certain house, and even if the physical distance if a few meters, if the only way is throught a one direction road that goes all arround the city, that house gets no hiospital cover. Also, the mass transit system is more realistic i think, you have to choose the circuit a bus line will follow, and where are they going to be stoping, etc. In that part, I like cities xl a lot more than simcity.
But what I dont like about cities XL is the economy part. It feels too artificial, with all that token thing. And needing to import fuel and stuff.. I dont know, in that area, simcity is way more friendly (enjoyable) for me.
Also, the overworld view of simcity, where you can see all your cities on a single big map like from a satellite, is what I miss the most on cities xl.
Oh, and I forgot, in cities xl you cant design your map, you have to play on pre defined maps (like 20 or so to pick). No god more terraforming like in simcity. A big bummer.