Art will never be good enough. It's especially hard on longer projects where you improve over time. I've hated every flash game I've released so far at some point.
Knowing that you can never succeed won't help you though, it'll still be just as hard to finish things. The only thing separating people who make art and those who don't is the simple fact that some people can finish things. It has nothing to do with inspiration or loving what you do, it's the simple fact that you just have to let go of it and allow it to suck at some parts. It always will, no matter how many times you restart.
Lobsterblues
I have the same problem. As a constantly improving songwriter, I find myself nearly unable to truly finish any song, since I always think it could be better both lyrically and musically.
I think it'll be better to just continue from where you are now, and move on to greater projects in the future.
Besides, you won't have the whole 'That last thing was my greatest thing ever. I'm never going to be able to create something better' vibe going on!
Just my perfectionist two cents.