It depends on the size of the game, and the content.
If it where Morrowind sized in quests and content and such, I would be happier.
Oblivion, definitely needed mods soon after playing for a while.
I would be very happy if they released proper modding support, TES construction set, and a plugin for Blender3D/3DS Max would be nice, etc.
Of course, if people down at NifTools where to make plugins like they did for Oblivion, I would be happy with that to.