I can't say I don't dig the weird look.

For some reason it makes me think of something I would see in one of the Mother games.
Good effort. I shrank them to normal resolution, copied the ones you finished into individual files, and tested them out.
The outline on this one doesn't really work, even when I used a black background.

It's hard to tell what's going on at all with this one. The colors are too murky and it's hard to read the expression.

The crying one is very hard to read and could use more contrasting colors.

This one isn't bad, but the shading on the mouth was kind of random; I edited it slightly.

While I love the expression, I can't tell if it's supposed to angry or confused. Also, the outline doesn't translate very well on brighter color schemes.

I think these two are the best overall, but I'm not sure what the expression is for the green guy. Yellow smiley guy could use some more polish.

Overall, the biggest problem is the outline--due to the AA, it's going to be hard to find a color scheme that looks good with all of them. You could minimize the problem by outling them like the green guy--its outline works with most colors I tried out.
I'd do a real edit, but pressed for time at the moment. This is good practice though. I hope you keep working on them. Maybe try more standard smilies, too?