I think there is a market for it, but I think that whoever creates an FPS these days needs to be a bit creative with it. For example, look what Half-Life 2 did (and, yes, even now this is a bit older, but it was created in the midst of all the hype for multi-player games, 3rd person perspective games, etc). What HL2 did is add a decent story line, added "non-traditional" FPS elements (like driving a dune buggy and a boat) and some decent narrative. So, in some ways, it seems the days of a simple DOOM game are done. People seem to want more than just eye-candy. But if an FPS is done creatively, then I suppose that it would do well.

I know that I am an "oldie" as well. I still like to play the original Doom, Quake and the original Unreal.