Well I guess pretty much every general concept has been done by now, but there are plenty of ideas which could make for amazing games, and currently, none of the ones out there are that great.
First of all, I believe this is true for war games. After reading about the Battle of Stalingrad, and watching stuff like Band Of Brothers, I don't believe any game really does the World Wars justice. I always found the Medal Of Honor games pretty tiresome. I'd love to see a genuinely great war game released that isn't so commercialised and actually makes you feel like you're there.
Secondly, I don't think there are any great zombie games, even though the genre has potential to produce something epic. Imagine, for example, a game in style to Oblivion or Fallout, but set in a world infested by the undead. That would be amazing in my opinion. Existing zombie games don't focus so much on atmosphere and evasion, more just blowing them to pieces.
Agree with these? Anybody have any other gaming ideas which you believe would produce something epic, or more obvious genres which should have produced better games than they have?