I actually think Octavarium is more consistent than FII since almost everything on the former is of low quality to me. Sure, some songs have moments here and there that are interesting (mostly the title track and Panic Attack), but overall the album bores me to tears. None of the songs are outright terrible, but I've always been quite unimpressed by Root (generic mid-tempo metal all around save for the chorus) and Never Enough (pretty much every section involving vocals = awful).
FII has some real low points (You Not Me, Burning My Soul, etc.) but it also has some of the best songs of their career (Lines, Trial, Peruvian) as well as some heartfelt ballads (Hollow, Anna Lee). Then there's New Millennium, which while incredibly happy is still pretty great. There's also the various B-sides that never made the album (but should have) like Raise the Knife and Speak to Me.