The best gameplay in Flash yet
I think I haven't reviewed something on Newgrounds in years, but your game is so great that I just had to.
The gameplay is just really smooth and responsive, which makes for an absolutely great and gratifying gaming experience. The fact that there are completely customizable controls is a huge plus, and everyone should always do that. Great selection on the soundtrack, metal songs which reminds more of the great MegaMan X soundtracks.
Here are the things that I would change or fine-tune:
1) Like some other mentioned, make Zero and the enemies "flash" for less time.
2) Since you can press Enter to enter the pause/Elf-selection menu, it'd be nice to be able to get out of it with Enter as well. Currently, we must use our mouse for that, and then move the mouse away from the gameplay area right after we clicked. Perhaps in the final version of your game, the whole pause menu should be "navigate-able" by using the keyboard.
3) It'd be nice to have an option to play at 200X size. Check out Megaman VS Metroid (newgrounds dot com/portal/view.php?id=124070 ) to see what I mean.
Otherwise, you got a kickass game, and since I suppose you're done with the engine, then you can tackle the fun part: make tons of stages!
To Atnas: there is a hard mode once you complete the normal mode. It also saves that you completed the game, so you can tackle hard at a later time. Although hard mode removes things like charging up the weapons and the sword combo...