Could the main Pokemon alone in begining of Decembre 2019 produce more sales than Smash + the 2 Pokemon remake + Mario Party ?
Too many people have made it a habit to overstate the impact of Pokémon on hardware sales. The way they talk about it, you'd think that Pokémon games have been selling 25m+ copies per installment, but the sales data shows otherwise.
Pokémon can be expected to sell 15-20m lifetime just like SSBU could be expected to, so Pokémon merely matches SSBU. Granted, Pokémon's initial sell-through will be higher than SSBU's, but its legs will be shorter because new Pokémon titles are released more frequently than SSB games. Similar lifetime sales, but different sales curves.