If FFI wouldn't do, then FFIX should be good. It's the closest to the foundation of FF and the latest to date. Plus, it's fun

My first FF was FFVI, but I want never able to fully appreciate the revolutionary turn (FFVI, FFVII, FFVIII, save FFTactics), introducing the none black mage, white mage storylines.

But whatever you do, I would highly go against introducing your friend with FFVIII. It's just not right imho =/ *casts flameshield* :P