If you're gonna release a sandbox game, at least give us a toolset so we can mod it. It extends its lifespan, builds a community around the game and lets fans carry the baton forward after you're done with it.
And sandbox has its place, but it isn't the be all and end all. There's something to be said for the Mass Effect way of doing things, the Deus Ex style of game. Tightly scripted, elegant and masterful level design is a thing of beauty. It creates immersion, fun and generally makes for a great experience. Open worlds have a place for sure, but don't neglect other greats, like the Sands of Time games or Splinter Cell.