IMO remakes are always done on already successful games, and the best they can do is a graphic overhaul and release... Probably a hard thing to get by, but what should be going on is scour entire game libraries and find concepts that are awesome, but the game turned out shit anyway... And correct those mistakes and make it awesome.
I think the problem is it's just too expensive to gamble on an idea, you have to play it safe or risk bankrupting your company. Therefore you make a remake of a hit that was already very good to begin with and people could just play that.
Same thing goes with a new game, look at what is already popular and do that again.
