http://truestofthetrue.blogspot.com/2010/04/five-of-worst-metal-videos-you-will.html
I know there are many non serious bands and parodies that have some awful videos, but I mainly stuck to mainly more serious metal bands. Most of these are classic songs, that you would have expected better...
I run a metal blog over at http://truestofthetrue.blogspot.com/
I mainly listen to NWOBHM, Traditional, Speed, Power(not modern euro) Thrash, Doom, and Death metal, but I listen to pretty much anything.