I thought it would make an interesting topic.
I would have to say:
7th Saga and Y’s for SNES.
Fallout II for PC.
The original Zelda (not Link I finished that one) and Bionic Comando (I got really close but never finished the last few levels) for NES
Finally Crono Cross and Parasite Eve for PSX.
I just never got around to finishing them before I found something else