Mine is Pokemon HGSS (the amount of content is mindboggling), Pokemon Platinum (grandest Pokemon experience) and Pokemon Black 2/White 2 (most fun and unique playthrough). I’m also looking forward to buying Legends: Arceus on the Switch, have heard many great things about it!
Right now, it’s scarlet and violet. Before that, it was legends Arceus. Before that, is was Sword and Shield. Before that, it was Sun/Moon. Before that it was X/Y. Before that…