I think the new one looks better, especially the orange person. The green and red ones still have their features in the exact same place though, and they're the two that have the worst sameface. Consider moving eyes closer together/further apart, or higher/lower. Same for the mouth and nose, even the hairline. With pixel art, 1-2 pixels can make all the difference. You could even have greater differences, if your goal is to make a varied cast of characters, rather than having them all be "ideally beautiful."
I also noticed the necks are all the same. Seems odd, given the effort you've put into making everything else not look copy-pasted xP I didn't notice at first so for general purposes it would probably be fine, but in a game where people might look at the portraits more than once, such things become easier to notice.
Lastly, their ears seem a little odd. The lit areas (the lobe and the large lit area below the rim of the ear) seem too large. Since the cheeks are in shadow, it seems that the ears should be more in shadow as well, with just a little bit of light.
Noted, thank you. I nuanced some of the existing details and slightly changed some things proportionally, as well as added some more details. How does it look now? Bottom row are the new ones
https://drive.google.com/file/d/0B2rrfVC7gIfyMkJ6d0VubndlLTg/view?usp=sharing
They all look almost the same because they have very similar features and identical proportions. Unless that's the goal, you should vary them up more. Right now, their hair and cheeks are about the only thing that varies noticeably.
Thanks for all the input. I really appreciate it, especially because I've never pixel'd anything like this before; it's usually simpler stuff dealing with less detail and stuff. I went ahead and made some changes with your critique in mind, and have now reuploaded the main image. I hope the new changes are enough to help differentiate the characters now! :)
I also made some more adjustments to just help things look better.