I know I essentially have no place talking here, being a lurker/newbie, but as a person who has done some pixel work before I wanted to comment on the large sprites vs. small sprites issue.
It's true that individual pixels matter more on small sprites than on large ones, but this isn't necessarily a bad thing. On a smaller scale, our eyes fill in the blanks more and we "see" something greater than the sum of its parts (which is really just a couple of colored dots). As the resolution gets higher, we get closer to actual drawn lines making up an image, at which point it becomes more difficult to just suggest something rather than explicitly drawing it.
Look at Ryu here:
It's cool to have bigger sprites, but the main reason of doing so is to also include more detail. It's true that you don't have to worry as much about how many pixels his nose has, but now you have to pay more attention to the folds of his clothes and the highlights on his muscles. You also will want access to more colors in more places, or it'll end up looking more monochromatic and bland. Also notice techniques like anti-aliasing on Ryu's edges; these things become more necessary as you scale up.
Essentially, your drawing, animating and coloring talents matter much more because now people can see it.
I also think space limitations are going to come into effect more than has been previously thought. How much freedom are your artists going to be allowed? NES era artists were always very conscious of the NES's limitations, and with good reason. You very commonly see squished or squared off images to keep things inside the boxes or at the edge of a color change. I think you'd be hard pressed to find a good artist who is aware of and able to function with the necessary restrictions.
Here's a really big NES drawing:
Not horrible, but clearly drawn with strict guidelines. Any awkwardness might be partially attributed to drawing ability as mentioned above. It might also be due to the grid, or it may be a bit of both. Every bit of fleshtone in those faces fits perfectly into a rectangle, and you can bet the space from the top of the eyebrows to the bottom of his nose is carefully calculated. Everything is specially placed to allow for the most solid color tiles possible. It's a big picture, but there's no detail. It looks like a coloring book.
Similarly here, you can see how Piston's arms have been forced into the rectangle. Notice the perfect horizontal line at the bottom of his gloves. And even with as few characters and frames as Punch Out has, they were carefully designed to have reusable mix-n-match body parts. Again, it's just line art filled in.
Is that sort of art good enough, or do you want it to look more like a real 90's fighting game?
Is it ok to just erase a guy's arm and then draw it straight out and call that a punch frame? If the artist wants to animate it realistically, are you going to tell him you don't think the lower body should move at all in order to save frames? If the artist draws the character's face two pixels out of the grid, is that acceptable or do they need to be shaved off? It all depends on how good you want it to look, and this should be considered in advance. Larger sprites are very tempting to trim for the programmer, and you need to decide early what you will and won't do. Smaller sprites are less of a concern here since the whole picture is crucial to the pose.
I am not trying to be discouraging, I just think these things should be thought through carefully. It's possible to make a great game with large or small sprites, but depending on how you do it things may be needlessly difficult. I understand well that anyone posting here would not deterred by the difficulty of something, but it may not be a type of difficulty that you're used to.
Personally I think the best idea is to scale down a little without going down to Mario size sprites. Keep it smaller than the max and your program is extensible. If you end up with space for three extra frames for each character, hey, that's one more special move per person, or some extra portraits and background art.
Also consider that if, for example, you shave off the top row of tiles from a proposed 6x9 tile fighter and make them 6x8 instead, that's 3 sprite tiles per fighter of extra colors. Is more height or more details more important?
On a different note, in terms of what I might offer, here's a guy I made. Single sprite overlaid for eyes.
Yes, he is somewhat naked.
But I don't know how much I could volunteer to this considering I am mainly here now to learn the programming side of things.
