Nintendo wouldn't have to offer relatively new full price games every month. How about that mix for $5 - $8 per month?
1 Virtual Console game (alternating NES, SNES, GBC, GBA), cross-buy for Wii U and 3DS
1 WiiU-compatible eShop game (smaller indie, 6 - 12 months old)
1 3DS-compatible eShop game (smaller indie, 6 - 12 months old)
1 Wii-game for the WiiU (perhaps alternating with GC-game)
1 DS-game for the 3DS
So if you only have one system, you get 1 new eShop game, 1 game of the last generation (first or third party) thanks to backward compatibility and 1 VC-classic (first party). If you own both systems, you get 2 new eShop games, 2 games of the last generation (first or third party) and 1 VC-classic (first party) compatible to both.
They could add 1 full price WiiU game per year to sweeten the deal... some good game with low sales like The Wonderful 101. And of course 1 full price 3DS game... perhaps something slightly underperforming like Yoshi's New Island or Sonic Lost World.
