I think SFAM is DT's greatest album, but it is a bit one-dimensional, so I can see why people might not agree. 6DOIT is great, but that title track is just too long, it bores me before I get to the end. 8VM is also brilliant, but there are some duff moments.
I love FII. If you like that more mellow, atmospheric side of the band (I do), they've never really done anything like it since. I can see why the OP would argue that FII is the band's last great album, but for me it has moments of weakness.
So, in conclusion, the last truly great DT album was - Awake.