Saw III was absolutely the worst Saw so far.

[The artist formally known]

I've yet to watch Saw IV in good quality but of what I've seen it was better.

Saw III Spoilers
[spoiler]Saw III was too much about the killers and it's terrible they killed off Jigsaw aka John because he was awesome but I'm glad the other person had died too because she was terrible[/spoiler]