EXPLORERS OF SKY. It's my favorite video game EVER. The story is lovely and has a fantastic balance of happy and sad moments and it GETS DARK AS SHIT. The characters are all really charming and the music and graphics are also amazing. Sky is technically the same game as Time/Darkness, but it has a bunch of extended storylines and one of them explains what happens to a character after a certain big scene and that you will definitely want to see that.
Gates to infinty (the new one for 3DS) also has a great plot/music/characters but it has some massive flaws in the gameplay (they took out gender selection for the north american release?? they never use pronouns for you but your partner is male by default it's stupid) and it also has an irritatingly slow start.
Some things to keep in mind if you end up playing sky:
You will most likely end up shipping your character with your partner (THERE IS A BUTTLOAD OF SUBTEXT LET ME TELL YOU) so you should choose names that won't make that too awkward.
The ending (several other scenes, too) is a massive tearjerker.
Monster houses are literally the worst thing ever so try and have a move that hits multiple targets.
The perfect apples incident will make you rage.
YEAH. PMD SKY. HELL YEAH.