You're Pixel Arts as they should be referred to as, are very boxy and malformed, as well as having no clear light source. Also, it's gotta pretty fucking uncomfortable to stand with your feet spread in opposite horizontal directions.
On the first one, the right arm, his right, extends much too far. It should not extend as far as the left arm, as part of it should be covered by the body. The jacket should not just suddenly end all the way around in a straight line right above the waist of the pants.
The shoes have been mentioned and the light source is fucked up.
For the second, the same problems are apparent, i.e. fucked up light source, uncomfortable feet, and generally sloppy line art.
I also find it odd how some things have a black outline, and some do not.
The third is just horrible. The main body has little shading, and that little shading is just thrown randomly about the legs and the bottom of the torso. The plasma effects look pillowed to me.
Your RPG sprites are okay, but have flaws of their own.
First, I'd like to say I love that FedEx box, but it needs more contrast. You can hardly see the shading. I am also confused as to why the back leg is completely shadowed out. It should be visible, but only use the darkest shade of grey and brown to color it.
Whatever the next thing, be a samurai, shaman, or whatever, is rather well done, but the hat stands out. Everything else has a black outline.
The next thing is outlined and shaded oddly, and once again, you shadow out one foot on the sideways sprites. Also, only one of the eyes should be visible on the sideways sprites, unless he tilts his head every time whenever he walks in that direction.
The next sprite is also out of style with the guy with the hat. No black outline, and the hood has no shading at all. I'm not too good at capes, so I can't really tell you if it's bad or good.
The shading on the final sprite's head wear is rather layered and doesn't look like cloth or a helmet. The shadowed foot actually makes sense on her, as you used the darkest shade for it. Her shoulders, however, are curved.
On the other sprites, the first one looks like a recolor of the example character from RPG maker.
The next two just have jagged line art and awkward shading or an unknown light source.