Others have covered the critiques as good or better than I ever could, and it's very impressive that you can take criticism well. That's how creative folks improve and it's great to see you seeking out peers for constructive help and suggestions. Keep doing that!
I just want to say "well done". These are a really strong start and it's plain to see you're extremely gifted. Now you just need to get some education and hone those natural abilities and you could honestly be a pro (if that's a goal of yours). Good luck and always remember that practice is the difference between a good artist who does their art as a hobby and a pro who does what they love for a living.
Incredible stuff. As someone who's always struggled with cities and architecture, I'm blown away with so much of this. Great character work too, obviously, but the buildings are really amazing. Nicely done all around. :)
I don't want to tell you your business, but Character Creation Contests are supposed to task the artists with creating an original character. All I see is you've mentioned Naruto and Sasuke (established characters). What is the creation you're wanting the artists to embrace? Invent a ninja to fight them? Invent a ninja to join them? Combine the two? What's the goal?
I like the idea of giving us some anime/manga to go from with any of the contests, but please provide a task you want entrants to perform with this. :)