Get Wii Fit Plus, Wii Sports Resort and Wii Play. Then I'd suggest New Super Mario Bros. Wii, Mario Kart Wii, Super Mario Galaxy, Super Smash Bros. Brawl, The Legend of Zelda: Twilight Princess and Metroid Prime Trilogy.
They are the titles you want if you like high quality gameplay. Metroid Prime Trilogy is a must though, all three titles for the price of one and all with awesome controls and fantastic gameplay. No other games quite like the Metroid Prime series.
There are also titles like Super Paper Mario, Punch-Out!! and World of Goo (WiiWare) which deserve attention due to high quality gameplay..
They are all first party titles (except for World of Goo) but there are many quality third party titles too coming soon but I'm sure everyone else will have you covered there..
