Have you tried
Craigslist yet?
It's a bulletin board-styled garage sale. People put their WTB or WTS notices up and you type in the word(s) you're searching for and it returns the nearest hits to you (based on the largest city you told it you live near). For example, if you live in Chicago, you choose the Chicago craigslist. Then you type in "Mega Man X" and hits may or may not come up.
The bad news is, you have to meet this person in person to get the game. (Just like with a garage sale, in theory.) The great news is, it's standard protocol to meet in a public place like a Starbucks or a McDonald's. It's also a better place to snag sweet deals because (a) a lot of poor people go on Craigslist and pawn their items off (vs. rich people who go on eBay and demand you meet their high prices or else you don't get it), (b) it's usually first come first serve so you're not competing with tons of other people for the same deal (which artificially drives up the price, just like on eBay), and (c) sellers don't have to pay any sellers' fees to craigslist (i.e. they keep every last dime that you give to them for the game), so many sellers are now preferring craigslist over eBay for any items worth less than $100 or for any customers who live close to them (since it could be cheaper to run an errand on that side of town and drop off the package while you're there than to pay UPS to mail it to the guy for $4).
Did you play the SNES as a kid or didn't you? If you played it, then you should already know what games you want for it. I'd focus on those and not get distracted by easier-to-find shittier games. If you didn't play the SNES much as a kid, though, then sure, here would be my recommendations:
Must-Haves for all audiences: Super Mario World, Super Mario All-Stars
Platformer junkies: Mega Man X, Donkey Kong Country, Donkey Kong Country 2
Adventure junkies: Super Metroid (platformer-adventure), The Legend of Zelda: A Link To The Past (rpg-adventure)
RPG junkies: Final Fantasy II (it's really IV), Final Fantasy III (it's really VI), Chrono Trigger
Fighter junkies: (Super) Street Fighter II Turbo
FPS junkies: sorry, bubs, a bit too early for that one.
RTS junkies: ditto. At least in America. Several popular RTS games for the Super Famicom, though. (Pretty sure the RoTK games of Koei's date back to the NES.) I suppose if you want to call Sim City an RTS you could get that. lol
Puzzle junkies: I liked Kirby's Avalanche. It was Hal's rip-off of Puyo Puyo with Kirby-themed characters. Or you could get Puyo Puyo 2 if Japanese carts work with American SNESes. I doubt it. But Puyo Puyo 2
ROCKS.
GameBoy owners: the Super GameBoy (converts your SNES into a GameBoy emulator so you can play GameBoy games on your big-screen TV. Only compatible with GameBoy and GameBoy Color cartridges)