If I had to rank the humanoid (sorry elcor and hanar) species from least humanlike to most humanlike, I'd say:
vorcha < krogan < salarian < volus < turian < batarian < drell < quarian (only because of the unmasked tali pic or I'd place them lower) < asari
I think... krogan < vorcha < turian < salarian < volus < quarian < drell < batarian < asari (duh)
The krogan are basically upright frogs...
Vorcha, turian, salarian have extremely alien looking faces, plus those backwards knees.
Volus is humanoid, just very small and stout.
Other than their backwards knees and three digit-hands/feet, quarians seem to have the exact same bodies as humans.
Drell and batarian have odd faces but otherwise totally human characteristics.
Asari are human except for the hair being tentacles, though I like to think they are more muscular than humans; I picture their "boobs" being mostly muscle instead of fat.