I'm glad to see you've been looking at Chesu's tutorials. They'll definitely help you hone your skills.
So, to start let's talk about outlines. Yours look bulky and thick because you're using more than you need. Most of the time when a line curves you should continue at an angle rather than with up/down, left/right connections. Here's an illustration to help explain:
You get a much cleaner line this way. Each of your sprites could be improved by smoothing out the lines this way. With a pokemon-style sprite an outline should also contrast with the surrounding areas (oh, and by the way, this also applies to other lines, such as eyes and mouths, not just the outside line work). Your yellow fakemon's outline is only slightly darker than the body so it's not easy to see.
As for the designs, they are pretty symmetrical and so look a bit flat. They don't have much in the way of shading either. The trainer's pants have some lighting, but it's in the center of each pant leg, as if the light were coming from directly in front of the sprite. A typical pokemon sprite has the light coming from the left and above so in general you should expect to see the left sides of sprites looking lighter and the right sides looking darker. You've done that in a kind of basic way, but the candle, because it's a cylinder, would have it's entire left side lightened. You only highlighted the upper left corner. Legs, arms, and torsos are also generally cylindrical so the same kind of shading should go on them. Really, you have to treat a sprite (unless it's a sphere like Voltorb) as separate pieces that might each need their own highlighting and shading.
You probably already know, but you have some weird proportions on your trainer. The arm with the pokeball is almost twice as long as the other arm (the distance from shoulder to elbow is about as long as the other arm) and there is
a lot of hair on that head.
Keep looking at tutorials and also look at the official sprites to see how they work. Good luck on your sprites.
