The rightmost set of eyes are good ... the upper fold of the eyelid is very important in giving the eye expression. It's something the upper left eyes seriously lacks, for instance, and makes it look dull and lifeless.

One thing I might suggest is a little less detailing on the BOTTOM of the eye. A single line defining the bottom is usually enough, unless you're going for a super close-up shot, and even then it's easy to overdo.

Overall, try to keep details to an absolute minimum. You really only need a few well-placed lines for most shots. And like I said, unless you're doing a close-up shot, anything more will look cluttered.

Added to that, You know what I should really do whenever I draw something I want critiqued ove rin the old scraps section?

Freaking number them...

EYEEEEEEE!

Sorry I took awhile to get back to you. I've been bogged down with essays and tech math, bleh!

I agree with zombie cat, the right eyes are good. They have simple lines and are defined quite well. The trick is to not overdraw the eye, which you managed to accomplish in those eyes.

However, making them too simple, like the other eye sets towards center left will leave them shallow and lifeless. You want to avoid that :-P

The eye on the top center (with the eyebrow) looks good though you may want to clean up the lower eyelid a bit. It has the potential to make the eye look mucky if there is too much detail/

As you can imagine, finding a good balance between complex and simple is somewhat difficult. Both are two opposite sides of the same coin, so one must think of the middleground.

Incidentally, I was just happened onto FA when saw my inbox +1 itself.