Not as grand as one would expect
I like the idea of a sprite collab, (I doubt this is the first, though) but there are several things that should be taken care of before making the sequel you were considering:
1. Sound. The volume fluctuated like mad between segments. When the viewer has to keep a hand on the volume knob just to keep up with how often the volume changes, that's just not good. All you need to do is watch the whole thing once and fix the sound if it deviates.
2. Set higher standards for submissions. Many of the segments you included in the collab obviously were not up to par with what is generally accepted as, well...decent. What tends to happen a lot in Flash movies is either the writing being great and the animation being crap, or the animation being great and the writing being crap. A lot of the segments in this collab were both (the crap part, I mean). It is pretty uncommon to find excellent writing AND animation in one Flash video, but you should at least make sure something is good about a concept before you include it.
3. Take your time and make sure your collaborators are taking their time as well. Even after you finish putting it together, take the time to tweak, improve, add, or subtract. It's the details that make a movie a movie. Now, I'm not a pro at Flash, but I am a video editor. I know that, if given the extra time, I could continue editing a video for hours and hours, just fixing the little things. And when you think you've got it, show it to some people just to get their input. If most of them think something is off, set it straight. Once you've done that and watch your creation, you'll know it came out much better than it was before.
Good luck on your next collab!