Tropico is really good. 3 will be dirt cheap, 4 is more an expansion but probably still worth the extra £.
Another decent alternative is the latest Cities XL, but it won't hold a candle to SC so just buy that when they sort the servers out.
edit: Cities is complex and not noob friendly unless you want to spend hours on tutorials. Tropico has some complexity to it, but by comparison it's very simple and you should be able to learn the ins and outs of it in a playthrough.








