Here's some fun games that I would recommend:
1. Super Mario Galaxy
2. Super Smash Bros. Brawl
3. Metroid Prime 3: Corruption
4. Mario Kart Wii
5. The Legend of Zelda: Twilight Princess
6. Boom Blox
7. Fire Emblem: Radiant Dawn
8. No More Heroes
9. WarioWare: Smooth Moves
10. Guitar Hero III: Legends of Rock
Congrats on the purchase and I hope you and your girlfriend have a lot of fun.