The list of games I DIDN'T beat might be shorter:
Resident Evil 4 on Gamecube. I rage-quit that one at the final boss battle. Nope. Never went back.
Loved that game so much but nearly put a hole in my TV over it.
Same here.
Ninja Gaiden for the NES. Got so pissed at it I tossed it out the window during a blizzard.
R-Type for the SNES... not sure why I never finished this one.
Shining in the Darkness Genie... this was stolen from me and by the time I recovered it a year later, my save game was, of course, deleted.
Quad Challange... this game sucked royally. This and some sort of RPG (Crimson Sword or some such) are the only two Genie games I ever got rid of. They sucked that bad.
Willy Beamish SCD. Lost many hours of gameplay due to bad save data in the internal SCD memory. Hosed all my save games but the WB loss was sinister due to the hours I put in. WB was the driving force behind my buying the memory cartridge. Point is, I was so furious I never tried to play it again.
Shining Force CD... play this one for more than a few minutes and you'll see why..... all battles and no RPG.
A large collection of GCN games were taken during a split. Forgot what was in there. Same for about half my PSX titles at the time.
There's been a few forgettable games. I never finished the Dr. Pepper shooter because the game has a game stopping bug preventing any further progress.
If I don't complete a title, it's because I just don't have the time to sit there and do it. Not really unbeatable in that sense. More like WIPS.