Earlier this week I read on the internet about a patch that allowed you to play Mega Man in Super Mario Bros! I was soon disappointed to find out that it was just a skin for Mega Man one that made some of the levels look like Super Mario Bros worlds. Not to put down the work of the author -- who did a fine job, as most of these redresses pretty poor -- but I was expecting exactly what my teaser title said. I want to be able to play as any NES character in any NES game, which would be so awesome! I can imagine playing Super Mario Bros as Ryu from Ninja Gaiden, or Mega Man in Metroid, or Simon Belmont in Kirby! What would be even more awesome would be tag team where you can switch between characters on the fly and play throug levels of all the great classical games on the NES.
I believe that companies read these blogs and get ideas from them, and I am sure that Nintendo could stand to make a mint on an idea like this.