I had a similar situation recently with my lady.
Ironically, one of the first recommendations I'd make is crazy party, ---- no don't all throw rotten eggs yet, let me explain!
The game has a bright and interesting soundscape, you don't need to learn a lot of complex keyboard commands or spacial directions or a learn game sounds menu, but can jump straight in and start playing.
What's more, the minigames serve as little tasters for a good many basic audio game playing concepts without being overwhelming. There are side scrollers like protect the duck, top down games, even puzzles and reaction tests, yet while some are harder than others, all are essentially smaller games that a person can pick up and play.
After all, which is better, getting frustrated with a complex side scroller like the gate which only has one experience, or trying out crazy party which has many experiences and lets you decide if side scrollers are or are not your thing.
Then of course, there is the turn based battle aspect, indeed after a bit of crazy party you'd be about ready to jump straight into something like manamon if you wished.
I would also recommend the esp pinball titles from draconis for an ironically similar reason, easy to pick up and play, not too heavy on the instructions and sounding great.
If your friend wants to get into some more complex first person affairs, likely gma tank commander would be worth a look, since you can always have fun with the exploding.
With our dreaming and singing, Ceaseless and sorrowless we! The glory about us clinging Of the glorious futures we see,
Our souls with high music ringing; O men! It must ever be
That we dwell in our dreaming and singing, A little apart from ye. (Arthur O'Shaughnessy 1873.)