I played this on your site before I discovered it was on Newgrounds, too, and it makes me a little sad to see that it might not get all the appreciation it deserves.
It's obvious that this screams Super Meat Boy and N+, seeing as those were your two primary inspirations, there are a couple of levels named after them, and even the character's design is somewhere between Meat Boy and N because he's a stickfigure with no apparent skin. But total originality isn't necessary to create a truly satisfying gaming experience, and there was a vast array of unique elements in this game that constantly kept it fresh and interesting. Those elements really added up and were used well, too--by the time I was done playing, SkullFace felt like no game I'd ever played before. The variety is amazing.
Heck, there are even a couple of things I prefer about this game over Super Meat Boy (like how the boss battle was handled, and how 'acrobatic' the main character is). This is really a well-designed game; I managed to beat each level with an A+ rank, and though it was difficult, it never felt unreasonable or downright cheap.
However, here's a list of my minor gripes:
I had a few issues with the wall jump right away, which stayed with me throughout the remainder of the game. I always longed for a bit more maneuverability upon leaping from a wall--as in, if I were to hold "down", SkullFace shouldn't jump as high, and if I were to hold "right" while on the left side of a wall, he shouldn't launch himself as far away from said wall.
I also think it feels 'off' that SkullFace slides down walls so sluggishly. It disrupts the fast pace of the game a little to be darting through sets of obstacles one moment and inching down a wall the next. Maybe the rate at which you slide down walls could have been based on momentum so the pace remained intact.
I found World 2 to be the hardest of all three worlds because I was still adapting to the way the game was meant to be played at that point, and certain levels (like 20 and 25) felt like sharp out-of-place spikes in difficulty. I felt a sense of accomplishment beating most of the levels, but those, not quite as much.
Also, the jellyfish-looking enemies in World 3 have what I consider a slightly over-sensitive hitbox. I would sometimes fall onto the edge of a jellyfish enemy's head expecting to bounce forward to a new part of the stage, only to instead explode into black squares. I soon "learned" the size of their weak point and had no problems utilizing it to progress through the game, but it was still a two-minute nuisance for an otherwise surprisingly 'non-frustrating' experience.
I was also kinda expecting a reward for getting an A+ on every stage. Even a "Congrats! You got all A's! What a great report card!" message on the main menu would have sufficed.
As mentioned, these are not significant complaints. They somewhat detract from the general polish and slickness of the game, but regardless, SkullFace is a highly enjoyable platforming game with (I'd say) more going for it than most Flash games that currently exist. The music is fitting and catchy, the artwork is crisp. the characters are memorable, the sound effects were entertaining and gave the atmosphere a special sort of 'kick', and it's just really darn cool sometimes (namely Level 28, 33, and some others I can't think of right away).
Simply put, even with its imperfections, SkullFace is a project you have every right to feel super proud of.