It's threads like this that make me feel completely and utterly invisible. After all the years I've spent hanging around here (not to mention other SF authors on this site), no one stopped to mention the optimistic SF works by those in your very midst.
Like so many other things, SF is not "all pessimistic," and many of the more prominent items singled out by the media were chosen by media executives specifically in order to give audiences a thrill. Movie audiences pay big bucks to be scared by monsters and conflict. We're being exposed to mostly pessimistic SF in popular media. That doesn't mean that's all there is.