Actually, when Sega stopped suporting the Master System, they put Tec Toy in charge of manufacturing and shipping it to the countries where it was still somewhat strong (I recall Greece being mentioned). They even made a custom Master System model, the Compact edition, that is like a screenless game gear, and connects to the TV wirelessly.
All their games works on NTSC systems, since Brazil uses PAL-M, that, besides being named "PAL", is much more similar to NTSC (60Hz).
Also, they actually didn't make the games... they basically imported the cart's boards, and made new plastic cases and boxes (translating the manuals, too). The content was identical to the US versions.
Only exceptios were the games they translated/modified. But those also works on NTSC systems.
The modified games (most SMS games) aren't "hacked". Tec Toy managed to license the game engine, and had freedom to change the content. Gameplay wasn't affected in most cases, but they changed graphics/story/themes to popular Brazillian franchises.
They also ported GG games to SMS (Gunstar Heroes, Earthworm Jim, etc...), ported Street Fighter II to SMS (with voices, and using a 8Mbit cart) and made a full game once (Woody Woodpecker, for Genesis - but it sucks).