Promising concept poorly executed
It's ok for a game to be challenging - otherwise it wouldn't be fun.
However the source of challenge in this game is the poor character control, numerous glitches (none of which benefit the player) and non-intuitive controls.
Mario World:
I only played this once. People attempt Mario game emulation on this site all the time. However, I think you did a good job with it, graphically. During the boss fight, I kept walking right through a shell I was trying to kick. Also, sometimes when I jumped Mario would take a little hop instead of a full jump, and that's unacceptable.
Mega Man:
Kudos for the cross genre idea. I dont' think it's unreasonable to only give mario 2 hits to defeat these bosses. What IS unreasonable, is the play control. It's terrible. Again sometimes I end up hopping when I am supposed to be jumping, and that always leads to disaster. Sometimes I fall right through the boss that I'm trying to jump on - that's just lack of you testing the game throughly. Some boss attacks such as Flashman are almost impossible to avoid. I think that I could beat a lot of these bosses if only the play control were at an acceptable level. Pharoah Man is the easiest. Drill man is the second easiest.
Gradius:
Pretty straightforward. As there is no jumping in this game, I can't complain about play control. Just move and shoot. The boss is poorly done. He appears not to take damage from my shots. It's pretty obvious you're supposed to shoot him in the center when he opens up, but there is no feedback that my shots are landing, they just disappear. I went through about 5 waves of that and just gave myself up. Games like these are all about powerups. Gotta have em.
In general: I hated your choice of control keys. They are non-intuitive and there's no way to change them. When I'm playing an emulator I use AWSD for arrows, / for B and right shift for A. Most Flash games are done using arrow keys for arrows, and either have UP the jump key or Space. The fire button becomes either Space or X then. Your controls were totally unlike either of those - you created a new idiom which doesn't work for me.
It's visually stunning. You have all the right graphics and all the right music. Nothing looks patched together or messed up like most sprite movies. This is why your game does as well as it has. As a game, I think it's pretty bad. I'd rather watch a sprite movie where Mario takes on all these different challenges and succeeds, than play this game and fail. And I like games, so that's saying a lot.
gc