I think 3 and 4 are probably the best paizo bestiaries. 5's not bad, I found it's PC to have some good and some bad (Android, Ghoran, really good. Skinwalker, deep One Hybrid, good. Orang, Reptoid, Caligni redundant to similar races. Shabti, interesting background that's not too likely to come up and too effectively human+. Astomoi just bleh.), but of the new planar groups, Manasaputra are ok (look cool but 'usually doesn't intervene in events' makes 'em limited), and Sahkil, well, 'grim reapers except evil instead of neutral, and really ugly,' is not something I think holds much of any weight among Pathfinder's other more interesting evil and/or destructive races. Oh, and robots, which IMO they didn't have a good enough selection of, though the Annihilator is a cool-looking beast.
And the rest, again a scattering. Some good, some eh, some weird. Not as much of a unifying theme as the last two.