Thats good to hear because I would hate for you to take what I say in the wrong way.
The first thing that comes to mind when I watch the video is that when looking at the screen as a whole everything looks flat, by that I mean non 3rd dimentinial. I think this is because of a couple of reasons, firstly because there are shadows in areas they should not be which tricks the eyes. The 2nd reason I would say is maybe most things are drawn in the Red/Green end of the spectrum and there is not enough blue in the picture overall. Maybe that is your intension however so this is just more an observation. Overall everything reminds me of how a game would look on the Atari ST.
So lets look at the shadows a little more closely. Now if we take the spheres in the borders as an example (top left corner), we can say the light source is top right of picture meaning all shadows should be on bottom and right edges in areas that are elevated. The borders are excellently drawn btw. When we look at the actual game play area (inside the borders) we can see the shadow is correct for the left border and the top border. However, you have a shadow in the play area inside the right border, In the real world this shadow would not be there and I think if you were to remove it it would improove the overall look. the same goes for the BG circle, there are shadows in some areas they should not be. In short, once you start using shadows the rules must be applied correctly and for all graphics drawn on screen. Taking this into account you could then use it also in areas behind the scores for example to give some depth. In short I think even if you just removed that one shadow on the inside edge of the play area as a test to see how it changes the overall picture you can then decide if you have to look at other areas also in relation to shadows.
Coming onto colors is a little more harder for me to comment on because this comes down alot to the overall feel your trying to create, because your currently in a limited area it makes some things not standout as much as they chould (the score). I think this could be addressed by altering the color used or adding a shadow into the font used (following the rules as mentioned above). Personally I thnk the ball you knock around may befifit from being pink. this is ala pink bullets in shooters.
As for effects, from what I can see in the boss videos it might be an idea to add a shake effect to the background everytime the boss gets hit. Not the borders or score areas though, only the bg in the play area (where large circle thing is). You could also play with pallettes to increase the effect when the boss is struck.
Given there is no trackball/spinner on neogeo I really like how you have used a force field as a helper because of the joystick. My only issue here is it appears to act in an identical way to the ball hitting the bat. I feel the ball should bounce off the shield at a random trejectory and again maybe play with a background shake or play area type flash to hilight the fact the forcefield hit. Maybe thinking about affects around the ball after hitting the forcefield might be an idea. I guess what I'm really getting at here is there needs to be a more noticeable difference between hitting the bat or the forcefield.
I hope this may have given you some ideas I would really love to see how it would look even if you have a look at how your using shadows. I might quickly knock up a picture of what I mean about shadows.