There needs to be a balance.
Nintendo in january 2013 is revealing yarn yoshi, SMT X FE, and xenoblade and those games are still in development, pretty much destroying hype as the graphics for those games are becoming less impressive by the day (when xenoblade was first revealed, it looked spectacular, but now that the witcher 3 and fallout 4 going by, Xenoblade no longer looks that great).
Nintendo in this recent e3 now only revealed 2 new budget games for the wii u this year and that's it. Not only did it make the whole conference look pathetic, but the future of the wii u looks dim for next year (whether it is or not remains to be seen, but I am personally convinced it won't be good).
So all in all, games should be revealed late in development if it is big or if there are other games to maintain hype for both the present and future. Games should be revealed early if there are other games to be shown in the near future, or if it has a genius concept that gets people's imagination working and maintains great hype for a console