Let's see the North American release years for the 3D home console games here...
OoT: 1998
MM: 2000
WW: 2003
TP: 2006
SS: 2011
Maybe we have been waiting a bit too long, but I don't know why. I don't know much about game development, but I speculate that SS took longer to make due to implementing 1:1 motion controls, which seems like it would've been difficult from a technical standpoint. Then of course we have the orchestrated soundtrack, which takes longer to make than a MIDI soundtrack because you have to worry about editing, mixing, and mastering. Before SS, Zelda used almost exclusively a MIDI soundtrack (exception: TP intro). I haven't even gotten into the time it takes to design the game world and character models, which may take 1-2 years in itself.
Regardless, I do think 5 years is too long to wait for a new console game. 3 years would be quite nice.