Here's a list I threw together of games they could (re-?)release with little-to-no-effort, offering all fans a selection of stuff that they virtually can't get elsewhere, while not costing Nintendo a dime.
Donkey Kong: Original Edition - 3DS or Wii VC
Previously only available when you purchased a select 3DS download title (in US) or the Red Wii (in EU). Features the "Pie Factory" level that was removed from the initial NES Release.
Mario Bros.: Original Edition - 3DS or Wii VC
This one would require a little bit of effort - it's a more better version of the arcade port - it was only released on the FDS in Japan and had a physical release on the NES in EU.
Super Mario Bros. 25th Anniversary Edition - Wii VC
Previously only available when you purchased a Red Wii in Japan. Has all the ? Blocks replaced with blocks that have the number 25 on them.
Doc Louis' Punch-Out!! - WiiWare
Previously only offered as a 2009 Club Nintendo Platinum reward. Lets you fight Doc Louis.
Grill Off with Ultra Hand - WiiWare
Previously only offered as a general Club Nintendo reward. Features a digital version of Nintendo's classic "Ultra Hand" toy.
Devil World - 3DS or Wii U VC
Never before released in the US. Released on both the 3DS and Wii U VC in Japan and the 3DS VC in Europe.
Any of the ten GBA Ambassador Titles - 3DS
Previously only available for individuals who bought the 3DS before the first initial price drop.
Legend of Zelda: Four Swords Anniversary Edition - DSiWare
Previously only available during one of two select time periods where it was given away for free.
Nintendo Video Downloads (Dinosaur Office Remix, Kirby 3D, Meat or Die) - 3DS
Each has been given away as downloads during Nintendo Video contests.
Of those, there's three things I want off of that list easily and would be offering folks $20 eShop cards in exchange for them. These could be offered in addition to any selection of VC/eShop titles that would make folks happy.