Funnily enough, I have a fair few Fallout project under my belt.
I've sussed my problem out, and it's probably the same for many developers. Basically I have this cool idea that I know will be awesome. I dive into development and get it well underway and then get to a certain point where either (a) it gets monotonous, (b) I realise the enormity of the work load to even get a demo finished, (c) it loses it's exciting sparkle and another project suddely seems more interesting, or most commonly (d) all three of those. It's rarely to do with lack of time. I can always find an hour or two most evenings, but I just can't be arsed because of (a) and (b). The current project I'm working on is suffering from a bit of (a) syndrome, but I've got (b) under control by having realistic goals (and help from Seppuku) and (c) under control by not bothering to think of new game ideas.
My significant unfinished projects list would be:
-Claymore Island
-Hover Racing V2
-Operation Desert Fallout
-Hover Racing V1 (although this was kinda almost playable demo stage)
-Bombardier
The only games I can claim to have totally finished were BFIF1 and 2 (Big Fat Ice Football). But they're unreleased because they have no single play mode. I made them at uni to play with housemates, so they're 2 or 4 player only, and the controls are weird (you need a joystick for one player, two on the keyboard and one on the mouse). I released one once but nobody was interested since they obviously didn't have any friends they knew in real life to play with.
So even though BFIF2 is a awesome (seriously, hours of fun and laughter to be had) and polished game, it's unreleased because you actually need real tangiable friends that you can touch and see and smell that actually come round your house to play it with.