Felt Like an Unrealized Video Game
I need to go against the majority here. This flash is good, but I can't say it is great. I will not give it a 10 just because it features so many NG characters from over the years. What worked best for me was the overall quality of the CGI. The character rendering was a great surprise. Movements were, for the most part, smooth and overall had a realistic feel to it. The fight scene between Gigantor and Mindchamber was nicely done.
What didn't work was the pacing. There was no direction to it. Most characters seemed to be "cast" in the flash only for the sake of appearing. The net result is that none of the characters get to do anything interesting. The "plot" of the flash is that characters fight to the death until there are two left, but we never get to see those deaths. Except for Gooseman. And it felt like his face time was because you had more than one line of dialog for him. Otherwise the viewer sees a fight start, but not end. The plot should move right to the point, rather than present the start of a fight and then just drop it. When you abruptly cut to the final fight, the viewer asks, "well, how did they get here?" Certain artists also seem to be disproportionally represented. I can somewhat understand that, especially in Tom's case since this is a Pico Day Flash. But having a character like Puppy from RAB, in full-on "Fucking Fucker" mode, or even Blockhead doing something completely nonsensical to win a fight over a superior opponent, would have added some much needed variety and humor to otherwise monotonous content. And how can you have a plot line surrounding King of the Portal without Strawberry Clock? Instead of truly feeling like a battle between "Warriors of the Portal," it felt more like pandering to the audience and particular artists.
Aspects of the animation that need improvement: There are several points where you can click on Easter eggs in the flash to view/change scenes, but none affect the outcome. This is fine for users who want the challenge of finding Easter eggs, but pointless otherwise. Instead of paying attention to the flash, users are clicking around with the mouse and mashing the keyboard. The images were rather dark and dull-colored and uninteresting to look at. And the voice work felt rather flat. I would expect characters in life-or-death situations to sound more animated. The viewer won't be invested in the action if the characters do not sound like they are invested in the action.
In sum, the presentation was great, but the potential of such an epic tale was never fully realized. I suspect a LOT of time when into rendering the characters as well as you did. But you didn't give those wonderfully rendered characters anything to do except to show up and then leave. Even if nothing else changed about the flash, simply showing a few seconds of the END of each fight, instead of a few seconds of the beginning, would have improved the quality drastically.
PS: I would have loved to see Mindchamber squash Foamy in about 0.5 seconds. But that's just me.