What makes a great game designer?
A great game designer is someone who's creative, pragmatic, good at problem solving, creatively problem solving and who is a good collaborator. A great game designer is someone who can work across the disciplines, who can work with the artists, who can work with the coders who are building the game for you and with you, and understand where they're coming from, and bring it all together at once. A great game designer is someone who can foster a good team environment, too. That's for a lead designer, at least. Level designers all have elements of that as well: good creativity, good problem solving, good ability to liaise with other people.