This is one reason I haven't paid any attention to the NES Classic. Certainly that would be cheaper, but not only is it non-expandable, Nintendo chose the games and only from (obviously) the NES library. Even there, where's 1942? And Double Dribble, Metal Gear, Faxanadu, Super Dodgeball, Joust, Duck Tales... and the first Contra?
If I saw a late revision 3DS w/ a couple of zeldas for $100, I'd grab that. And I could skip the upcoming Gameboy Classic, Gameboy Color Classic, SNES Classic, Gameboy Advance Classic, N64 Classic releases too.