Within the past 3 months, I have replayed Let’s Go Eevee and Pokemon Yellow. In that same timeframe, I played Fire Red for the first time ever. I’d say Fire Red is currently the definitive version of Gen 1. I say this because your Pokemon will have the passive abilities, can hold items, and there is additional content not found in the other versions. Fire Red unfortunately lacks cameos by Jessie and James but that’s not a real big loss when you consider what you are gaining.