For me Twilight princess is the best zelda game to this day, I just loved that game, can't explain exactly why...If he has a 3ds he should get oot, a link between worlds and a link to the past. But I dunno if op has a n3ds or even 3ds so he can play those. Anyways those are my top three non botw (botw is #1 for me overall) Zelda games that I've played so far.
Then in 2nd place these:
Minish cap - or Skyward or Majora's or Wind Waker (order explanation: most likely to be 2nd place if I had no options on the left, less likely on the right)
3rd (Same As Before)
OOT, BOTW, ALTP, ALBW,
4th (SAB)
The gbc ones (... )