Nothing will probably ever top ROBLOX for me. Rating sandbox games- or really any game which largely leans itself on user-generated content - is a bit weird because the line where the developers' skill ends and the content-makers' skill begins is always a bit fuzzy. But ROBLOX seriously did an amazing job here, it's a great place to learn code, graphic design, all sorts of cool creative endeavours. I owe a staggering amount of my development as a person to ROBLOX, the people I met on it and the things I made on it.