I would have to say Fresh. I remember playing that all the time before I started my own. Great staff and community on there but the economy kind of sucks. They give out too many creds.
success has nothing to do with the future of it. MySpace was a successful website, but at one point it stopped being popular and some other site took its place. One day Facebook will be past, but that doesnt change the fact it was once successful.To be honest; none.
One day ~ all those known retros will also go in an end. Nothing or no retro is permanent. They will loose users when they start getting bored in all of what they give.
I think Static Hotel was Blah Before ....