Okay well, I found it. Eh, PSUs are much better for a tier list, because the motherboard tier list is basically like "These units are fantastic, these units are semi-fantastic, these units are great, these units are good". Plus value is not a factor. Basically, everything is quite good when it comes to motherboards, though I can name a couple (SLI Krait) that come to mind as poor.
The major difference in the PSU and motherboard tier list is that the PSU list has definitive units you should not buy, such as tier 4 and below, but the motherboard tier list is basically everything is good and better. So really, loses its purpose, because value is much more a factor when it comes to motherboards and budget, whereas with power supplies quality is more important typically than value.