The new Donkey Kong Country: Tropical Freeze trailer is going to be amazing! I should stop giving that game a hard time, especially since I enjoyed Donkey Kong Country Returns and Tropical Freeze looks better.
If there is going to be no new game announcement and just a new trailer for a previously announced game, then I guess that's okay. A new trailer for Super Smash Bros. for Wii U won't be exciting, but it will be nice. If there's a new trailer for X or, I don't know, Fire Emblem X Shin Megami Tensei, that will be a pleasant surprise and a perplexing shock.
I've been thinking about what would be a unexpected and underwhelming announcement. Minecraft for Wii U fits that bill for me.