I voted for a Bubble Bobble type of game. I think it's the easiest kind of the bunch. Others would need tons of graphics and coding. Better start small at first.
Also... I just LOVE Bubble Bobble

A Zelda type of game should be fun and doable also...
And maybe something turn based logic/strategy like "DNA The Variety of Life". Now that's a AWESOME game, yet... with simple mechanics.