Judging whether Pikmin and Pikmin 2 is a commercial success or failure is not an easy process.
The anti-Miyamoto/Pro-Sakamoto crowd will say in light of the success of Miyamoto's other Nintendo brands, Pikmin and Pikmin 2 are failures because they did not sell as well as a Zelda or Mario game. Especially since Pikmin 2 sold less than the original, which means the series is a dud with a limited audience who could not push a Pikmin 3 over 2 million copies sold.
The pro-Miyamoto crowd would argue of course the Pikmin series is a success. Miyamoto created a third-person RTS simulation type game and the fact both sold over 1 million copies shows just how much of a creative genius Miyamoto is. The creator of Megaman (Keiji Inafune) and Metroid (Yoshio Sakamoto) have not created a game outside of their hallmark series that has sold over 1 million copies. If Sakamoto and Inafune who have created 2 of the most iconic video game series cannot replicate Miyamoto in creating a series where the original and sequel have sold over 1 million each, then who is the barometer for commercial creativity success? Name me another famous developer besides Miyamoto who has created 3 series with at least 2 games in each of the series selling over a million copies.
Personally, I think it is a mix of the two. Yes, I agree in comparison to a Zelda or Mario game, the Pikmin games sales have been underwhelming considering it is coming from Miyamoto. Then again, considering that Pikmin is almost in a genre of it's own (third person RTS), both Pikmin games selling over 1 million is evidence of the weight Miyamoto still carries to this day.