Is there any instance when you go back and look at something you've read or written where you tend to be surprised at how good or bad it actually was in retrospect? Meaning the first time you read it, you thought it sucked but on the second reread, suddenly you found it awesome or vice versa?
Some of my favorite stories are ones that took me two tries to get into. Cover Me With Dreams and Between the Lines are the two examples that come to mind. They both had come highly recommended, but because they are both genres that are not my favorite thing and had elements that turned me off, I didn't get very far on either of them the first time I tried to read them. It wasn't that I thought they sucked; I just didn't get sucked in until I forced myself to read farther the second time. There came a point with each of them when I did get sucked in, and now they are two of my favorite fanfics of all time.
At the same time, there are also stories I really liked early in my fanfic-reading days that I reread years later and didn't have the same reaction to. If I read them for the first time now, I probably wouldn't add them to my favorites list. My taste in stories hasn't really changed, but my tolerance for poor writing has thinned.
With my own stories, I find that while I usually (hopefully) like them while I'm writing them and immediately after finishing them, that feeling only lasts a certain number of years, before I move on to better things and realize the old ones pale in comparison. On the rare occasion I reread something I wrote more than a few years ago and think, "Wow, this isn't that bad," it comes as a pleasant surprise. Most of it is pretty bad LOL.