NES: Super Mario Bros., Super Mario Bros. 2 (Lost Levels), Legend of Zelda, Kid Icarus

SNES: Super Metroid, Link to the Past, Super Mario World, Secret of Mana, Gradius III

N64: Yoshi's Story, Star Fox 64, Super Mario 64, Mario Kart 64

Neo geo: Samurai Shodown

Genesis: Sonic The Hedgehog 2, Golden Axe II

Probably a couple I'm missing

I have a good number of the games on VC in original cartridge form, so I don't really feel the need to buy them again for myself.  That being said, I bought some on my family's Wii.  I didn't buy them anything hardcore like Megaman, but what I did buy was:

Super Mario Bros. 1, 2, and 3
Sonic The Hedgehog 1 and 2
Super Mario World
Super Mario 64
Zelda Ocarina of Time

Each game gets a ton of playtime.  Everyone has allot of fun with them, just as much fun as if they were on the original console.  Let's face it, the VC is awesome.
If I were to buy them more, I'd probably buy Kirby and Donkey Kong Country.

For Wiiware I only bought myself Megaman 9.  I loved it, and caved in to buy endless and the harder difficulties.  I rank Megaman 9 up there with Megaman 2 & 3.  I like those 3 equally.

Ha, cool topic idea...even if it is fairly old, haha.  Here's my list thus far:

WiiWare:
Strong Bad's Cool Game For Attractive People Episode One Homestar Ruinner
Strong Bad's Cool Game For Attractive People Episode Two Strong Badia The Free
My Vote Channel
Photo Channel 2.0

Future Purchases:
Final Fantasy IV The After Years
PoK'eMoN Snap (maaaaybe)
Paper Mario (FO' SHO'!)
Sin and Punishment (if it's worth it)
Super Mario Bros. 2 The Lost Levels

and not that you asked, but here's my PSN list:
Linger in Shadows
Metal Gear Solid Database
Ragdoll Kung Fu (got it for free)
Syphon Filter
Crash Bandicoot
Street Fighter Alpha
Resident Evil Director's Cut Dualshock Version
Final Fantasy VII

The only reason i do it is that it is conveniont.

So far, I've bought

NES: Kid Icarus

SNES: Zelda: A Link to the Past, Street Fighter 2 Turbo

WiiWare: Mega Man 9, Dr. Mario RX (My fiancee loves this one! She kicks my butt in it everytime we play.)

Looking to buy: Gunstar Heroes, Splatterhouse, Contra 3