I keep starting Secret of Mana on my SNES but never getting that far before moving to something else. Had Twilight Princess since I got my Wii, still never really got far with that and I kind of lost interest in Metroid Prime 3.
Really it's only Secret of Mana that I have had problems with as I generally start a game when I get it, get quite far and then just stop. For example I did that with Fallout 3 which I bought at launch for full price (
oddly enough when Steam games were in dollars) started it but then left it for two years before actually completing it.
I think the only games I haven't completed in my collection which I am not currently playing are Secret of Mana, Twilight Princess, Metroid Prime 3 and the Witcher 2 which is actually a little too much for my 6 year old PC to handle. So I'm quite happy with that. I'm playing Xenoblade Chronicles and Tactics Ogre at the moment and they are both going to take weeks to finish.