Simple solution: Save some cash and invest in one of
these for NES and one of
these for SNES.
They will alow you to play literally all games ever made for each system but 10 or so games for each system (only games with special chips besides SP1 are not supported on SNES Powerpak and NES only Pirate games and Castlevania III have issues) and will be SO MUCH cheaper than buying all the games I am about to recommend. Start your collection AFTER buying these, because these will also allow you to play all those magnificent import titles (Terranigma, Bahamut Lagoon, Final Fantasy V, and so much more) on real hardware.
NES:
Mega Man (series, 1-6)
Also try some Mega Man hacks
Earthbound Zero (there is an easy patch to use for it to be more bearable)
Final Fantasy (1-3)
Castlevania (I-III)
Super Mario Bros. (1-3, again, try some hacks for even more content)
Silver Surfer (for angry lulz)
Metroid
Kid Icarus (will piss you OFF)
Action 52 (lol just kidding)
A Boy and his Blob
Adventure Island (series, 1-4)
Advantures of Lolo (series)
BATTLETOADS
Bubble Bobble (1 is easy to find, 2 can get REAL PRICEY)
CONTRA
SUPER C
Contra Force (you can pass this one up, it's rare and the other two are better but if you're Powerpakin' it no biggie)
Double Dragon II
Dragon Warrior (series)
Famicom Wars (with english patch; ADVANCE WARS for NES)
Galaga
Ice Climber
Kirby's Adventure
The Legend of Zelda
Zelda II: Adventure of Link
Metal Gear
Ninja Gaiden (series 1-3)
Street Fighter 2010 (for a challenge)
YOSHI'S COOKIE
Yoshi
That's for starters...
SNES:
Donkey Kong Country (series 1-3)
Chrono Trigger
The Legend of Zelda: Link to the Past
EARTHBOUNDEARTHBOUNDEARTHBOUNDEARTHBOUNDEARTHBOUNDEARTHBOUNDEARTHBOUNDEARTHBOUND
EARTHBOUNDEARTHBOUNDEARTHBOUNDEARTHBOUND
Fire Emblem (series, english patched on Powerpak. BEST game of the series is on SNES)
Harvest Moon
Lufia (series)
Mega Man X (series, 1-3)
Mega Man 7
Star Ocean (english patched on Powerpak)
SUPER CASTLE-FRIGGIN-VANIA VI (BEST CV game ever)
Super Mario World
Super Mario All Stars
Ninja Turtles: Turtles In Time
Zombies Ate my neighbors
Ghoul Patrol
Super Mario RPG
Ninja Gaiden Trilogy
Terranigma (Powerpak only)
Final Fantasy II (ALSO KNOWN AS IV)
Final Fantasy III (ALSO KNOWN AS VI)
Final Fantasy V (English patched Powerpak only)
Yoshi's Island
Super Metroid
Super Mario Kart
For starters...
TRUST ME! The Powerpaks are worth the investment. The price of Earthbound (my favorite game of all time, MUST PLAY) and Final Fantasy II equal that of the SNES Powerpak alone. To be able to play the entire NES and SNES library for 280 bucks a such a deal for a retro gamer... I would buy them before Retrousb goes out of business one day. They'll only appreciate in value from there, too, since they are the only ones who produce them (Owner of the site makes them all by hand).
If you need help with ANYTHING retro I can help you, I am so big on retro games.
Just shoot me a PM and I can help you with anything (Even modding your SNES to play Japanese games; its A FREE MOD TOO LOL) doing with oldies.