To me, very few parodies are good. But some are (sorry I don't save jokes forever just in case I might want to link them later so I don't have examples).
A good parody thread has these:
1) Originality - not just changing one word to get a point across, but completely revamping it while maintaining the same form and structure.
2) Humor - makes me laugh.
3) Has a link to the original thread (to avoid confusion and to highlight the humor).
Sadly, almost all lack #3. And sadly, many lack #1 or #2.