SG-1000 games do not display proper colors on Mark III and Master System consoles. (they do not display at all on US Master System consoles)
I highly recommend (My Card) MC Champion Billiards and MC Champion Boxing. The billiards game has some catchy music (by Compile) and controls nicely. The boxing game has some huge characters for the era and offers up a strategic challenge and unique interface whereby one button chooses the type of punch to throw and the other throws the punch.
Sega Galaga is quite fun, but pricey.
another costly item is the Terebi Oekaki [Sega Graphic Board]. This thing has a small glass window which you can place an image underneath and then trace over, recreating it onscreen. Of course you can make freehand sketches too. The board I have requires that I press quite firmly and the accuracy is usually good but it does regularly stray from where I mean the cursor to go.
Another super early Compile game worth checking out is MC C-SO! It's a single screen game where you run up and down ladders avoiding enemies and collecting fruit, and you can use teeter-totters (see-saws, hence "c-so") to kill the enemies.
last but not least, MC Choplifter is perfect.
I can also recommend the following:
Hustle Chumy
Monaco GP
N-Sub
Pacar
Pachinko II
Pop Flamer
Safari Hunting
Sega Flipper
Sindbad Mystery
Star Force
Star Jacker
Yamoto
Zippy Race
Othello Multivision
Space Armor (most annoying music/sfx)
SEGA My Card
MC Bank Panic
MC Bomb Jack
MC Chack 'n' Pop
MC Dragon Wang
MC Elevator Action
MC H.E.R.O.
MC Monaco GP
MC Pit Pot the Magical Castle
MC Pitfall II The Lost Caverns
MC Star Force
MC Super Tank
MC Zoom 909