I'd say Mario 64, followed by Wii Sports and Mario Bros. ranks third. All those games defined the platforms they were on, but Mario Bros. was not worldwide and Wii Sports shows not all of the Wii's capability.
I'd say that the Wii has the best launch games, because the duo Wii Sports/Zelda: TP is nearly unbeatable, it appeals to a lot of people. But as a single game, Mario 64 was more important.