Keith Courage and China Warrior would have cost like, 5$ total. Hell, does the guy post on here? I'll mail him a loose copy. I think I have two.
As far as introduction games, its great for many reasons.
1) It's not like OMG FAST PACED REFLEXES OR YOU DIE HAH f*ck YOU. It's mellow. You start off in town and derp along to the funny town music and get a feel for everything.
2) You get to the end and a rainbow shoots down and you TRANSFORM THE f*ck OUT. That little scene where you morph, f*cking rules.
3) Once you drop into the underworld, holy shit. Mutant capguns, frankenstein bullshit, multiway platforming. And it's still not OMG PRESS FASTER YOU PUSSY, YOU'RE DEAD IF YOU DON'T. The boss-battle room looks cool as hell, and the music it plays is intense and exciting.
The whole time, you are treated to pretty smooth graphics. The shading of everything is pretty nice. The sounds are great too. That sword-swing in the underworld sounds awesome. I always liked that loud ass "whoooompah" noise.
It showcases just about everything the system can do: Sweet music, solid controls, big and little sprites, and pretty colors.
Plus, it's not like "oh, its only good because its cheap". The game was f*ckin free. You got it just for buying a Turbob.
My suggestions to a Turbob N00b are as follows:
China Warrior
Bonk
Neutopia
Vigilante
Keith Courage
Blazing Lazers
My ultimate reason? This is what I was exposed to growing up on the system, and it was enough to make me want to program shitty games for it!