Just one?
Skies of Arcadia.
literally came to this thread to say that exact game. i never would have thought anyone on animal crossing would ever say that game. i have it for dreamcast and the legends version for the gamecube. if a hd remake, remaster, sequel, or anything else of it came out i would buy that too just because it's a great game. literally one of the best rpgs on the dreamcast without a doubt.
Pok?mon SNAP! omg a HD remake would be amazing.
Outside of Animal Crossing, I am all about RPGs...and I've been in love with Skies of Arcadia since the Dreamcast release. That, Final Fantasy IX, and Lunar: Silver Star Story/Eternal Blue (I count them as one since the storylines are pretty closely woven together) are probably my favorites of all time.