The Portal games are good, but I don't think they help someone get into gaming. They're too unique an experience, so when someone finishes they have an idea of how Portal works, but are no closer to understanding how gaming works.
I'd suggest either a co-op shooter like L4D2 or Halo 1 (FPS games are surprisingly easy for new people to get into and they show off the medium quite well). Another option if they're a fan of Disney is Kingdom Hearts. Or my top choice, Paper Mario.
I'd suggest either a co-op shooter like L4D2 or Halo 1 (FPS games are surprisingly easy for new people to get into and they show off the medium quite well). Another option if they're a fan of Disney is Kingdom Hearts. Or my top choice, Paper Mario.