1. Legend of Zelda - A franchise that never disappoints, always enjoy going back to the older versions and can't wait for the new ones.
2. Metroid - Surprised it hasn't been mentioned yet, the series is just incredible, love the exploration and upgrading Samus with new weapons and skills.
3. Mega Man - Original series, not X or anything like that, pure platforming fun, so glad they're releasing new titles for download
4. Super Mario - Without Super Mario there would be no gaming industry today, also the franchise that showed how to make 3D games work on consoles
5. Ratchet and Clank - This is just a fun series and one of the main reasons I'd buy a PS3.