Nintendo is currently running a sale on the eShop for which the title explains it all: Two Games, $2 Each, Two Days.
Two Mega Man games are being offered at a discount during the current two-day period, from noon ET today through 11:59 a.m. ET Dec. 18: Mega Man: Dr. Wily's Revenge on Nintendo 3DS (regularly $3.99) and Mega Man X (reg. $7.99, screenshot above) on Wii U.
Capcom originally released Dr. Wily's Revenge on Game Boy in 1991. Mega Man X was first released on Super NES in 1993 in Japan; it came out in North America in 1994.
Keep an eye on the Nintendo eShop's Special Offers page to see the next set of deals when they go live at noon ET on Wednesday, Dec. 18.