The good points I'm sure you can see for yourself
The only way to improve is through constructive criticism - and I'm giving it to you because you have a lot of potential. Let's start with the major most annoying things 99% of all good video games have in common.
1. FUCKING LET THE MAIN CHARACTER HAVE THE ABILITY TO JUMP OPTION DAMN IT. There are too many games in which the characters are refused the ability to jump. He has legs to run - at least let him be able to jump, too! It's not that hard to draw him jumping is it? Why won't so many video games let the player jump Is it really that difficult? What kind of character that has legs can't jump? If we were attacked by falling magma and it's about to attack us, we could consider jumping, too!
2. Let the character have an attack option or something. Guns at least - I know you're trying to make him run, but you could, for starters, as the game progresses, make his self-defense improve - it's called evolution or more commonly - power ups. I know you have some power ups, but I'd like a leveling up more like it. For instance, after every 100 seconds you survive, you get a new weapon in which you could fire at magma to destroy it. 3 power-ups are a bit limited.
3. Okay, so aside from the "jump" (which is what I had to say or I'll go crazy), you could give the character more flexible commands. Ducking, weaving, somersaults, sliding, etc. Just being able to run is a bit too limited. Explore more options - I know your 3 Power Star episodes, and I know your ability to animate is amazing. You could pull off more stunts than just running, come on man, I'm expecting more from you.
4. Plot - well, this is optional, because this game is for a simple design really. At least make an intro flash or something. Like say the kid was running away from home, and then he got stuck on a mountain, and suddenly magma started raining down and he wants to get out of there.
And aside from the parts you need to work on, I must say - I laughed my ass off at his facial expression. I'll never forgive myself if I couldn't compliment you on that.
Oh, and btw
WHERE THE HELL IS POWER STAR 4?!!!!!!!!!!!!!!!!!!!!!!!!!