Well if it's the original version that takes the cards, hold on to it. Those are going to be worth money some day.
As for actually playing it.... umm... aside from Wonder Boy there's a decent boxing game...Ring King?.....Sorry I've got nothing....
The main reason the SMS wasn't successful is because at the time Nintendo made all companies producing games on the NES sign a agreement saying that they couldn't port the games to other consoles. So all of your classics from the era... they are on the NES. What's left are in-house sega games (some good, some terrible) and obscure third parties that weren't big time enough to produce on the NES yet.
Yeah like Mortal Kombat II, Ninja Gaiden, Rocky, Rambo, Gauntlet, Baku Baku animal, Klax, Outrun, Asterix, Golden Axe, Choplifter, Terminator, Kung Fu Kid, Bonanza Brothers, Batman Returns, Streets of Rage, Buggy Run, Darius 2, Space Harrier, Desert Strike, Road Rash, Marble Madness, Alex Kidd in Shinobi World (reminds me, Shinobi is on the master system, but it sucked), Golden Axe Warrior, Fantasy Zone, and R-Type.
I admit a lot of those games are better on other systems (specifically the Genesis/SNES/Arcade) but to say the SMS didnt have a little bit of merit seems short sighted. Lets not do the whole "no point in playing it on a console if you can play it on your mame cab" song and dance, kk? I think we can all agree that Krusty's super fun house sucked on all the systems.
I would LOVE to have a SMS, never got one as a kid, cant find one at a decent price as an adult. Thought about getting a power base for my model 1 genesis, but no luck with that either.