Nationstates was ok for a bit. But it has a very simplistic model and nothing much happens unless you decide to engage yourself in a totally made-up pretend world and join fellow players who wish to go around playing pretend games like you're still a child in school. Which gets boring fast. As do the hundreds of stupid invites to stupid non-important regions which are owned by stupid 11 year olds. I think my nation reached about 1.3 billion population before I abandoned it. Really I'd like the whole economic/social/political model revamped so you actually have to put some effort into maintaining the state of your nation. A few simple 'issues' isn't enough. Zero tax or 100% tax makes no difference for example.