I love the Sega Master System too. The system itself is more handsome looking than the NES and gives you less problems (no blinkies). And the graphics are brighter and more colorful.
But still, the NES's game library beats the SMS's game library, EASILY. Wonder Boy and the Sonic the Hedgehog SMS may be cool platformers, but they've got nothing on Super Mario Bros. 1-3 and Duck Tales 1 & 2. Golden Axe: Warrior wishes it was as good as the Legend of Zelda and Crystalis. Zillion is pretty cool but I'd still take Metroid over it. NES's Ninja Gaiden may not look as good, but the gameplay is 10 times better. Sega Master System got R-Type over the NES, I'll give it that, but then at the same time NES got Gradius and LifeForce and SMS didn't. There's nothing on SMS to compare to the Castlevania series, Mega Man series, Contra, or Bionic Commando among others.