See I like to take my video games seriously. None of that Mario dick nazi crap or some such other silly nonsense.
Total conversions. On the serious tip.
Like say, for example, that new Metroid Rogue Dawn hack that is coming out. Now that is some enspiring stuff. It's making me want to begin on my own idea that is quite different but just as big. Or maybe the Castlevania III hack Vengeance on Hell. You know, serious type shit.
It kindof amazes me that nobody has made a Metroid hack with vastly edited palette blocks (aside from Rogue Dawn which doesn't count because it's pretty much the best T[otal] C[onversion]. Most Metroid hacks I've played still use the same graphics blocks. Go figure.

So sprite editing is what I mean. Editing sprites in the 8x8. (Plus palettes of course.) Then there's music (of course that's always good.) But that and gameplay mechanics. This is something people probably don't do because it's just too hard. (and there's help here on the forums but it just isn't enough apparently.)
So - total conversions of good games. Those with good ideas could easily come up with enough to satisfy at least many more than has been released as of yet.
It seems to me that , as of yet , the ideas category is lacking as is the the will to actually do hacking on a massive scale.