The greater danger for most of us lies not in setting our aim too high and falling short; but in setting our aim too low, and achieving our mark.- Michaelangelo
I think it's quite useful to differentiate between the absolute scale and the relative scale when judging something. As an example, take Microsoft Word. It's probably true that Microsoft Word is the best word processor you can buy right now. That is a relative judgment...there are no other word processors you can buy that are better.
However, it is completely false to say that Microsoft Word is the best possible word processor you could create today. In fact, on that absolute scale, it's not that great at all. You can't use it for more than two minutes without running into 20 things that could have been better, things that shouldn't have happened, or missed opportunities to do something cool and useful, if you approach the problem with fresh eyes and an open mind.
We should be shooting for excellence on the absolute scale where possible. Doing something that's merely better than the other stuff around is sort of a cynical approach to creating things, don't you think?
Ignoring the absolute scale and only paying attention to the relative scale often leads to the good enough problem.