Sometimes, but that feeling usually dies once I actually play it and realize "holy shit this stinks"
e: Last time I did it the enemies died in one hit then they kept attacking me from beyond the grave which was funny after I dug through the code to fix a bug that I left no documentation on or anything
I unearthed a game I started a couple of years ago called Mother 9: Exodus of McDonaldland where Lucas from Mother 3, Shrek, Grimace, and Fred Flintstone team up to save a broken dystopian McDonaldland drifting in the void.
I handed the project off to someone else who wanted to finish it and have not heard from them since.
I've done this, though I'm pretty sure we all have :P
Sometimes though it's scope and poor planning, delusions of grandeur and overwhelming thoughts of like "where do I start?"
I used to have this bad habit of doing a shit ton of mapping and event placement but when it came time to do dialouge, items and combat it became scary and I would stop. Which is a shame because those things aren't hard but it is a whole lot more work than mapping (at least to me)
Some of them were fan games that were probably pretty decent but I got to that point where I figured I'd rather be doing my own original idea.
It's also a case of "this sucks or has the potential" but back then I was also flakey on projects and would get an idea and move on. And it's probably for the best most of the time because if you feel no love for the project then it's usually best to move on. :)
It happens and sometimes it's fun to go back and look at the past and even may be reignite a game back into reality.