I voted for the winner.
My apology:
#1 looks quite cool but doesn't have the wow effect like #3 has
#2 looks a bit toony
#3 looks awesome
#4 shows great rendering skills, but designwise it's poor
#5 lacks color or shading, not good for a presentation
Please don't be offended, it's just positive and honest criticism.
Also I'd like to join the next competition as well as I would have liked to join this one, but unfortunately I haven't found the time to work out and even render a design.