Perfect Debute Albums

Oasis - Definately Maybe
Hootie & The Blowfish - Cracked Rear View
Adele - 18
Mumford and Sons - Sigh No More

Also, re The New Radicals....frontman Greg Alexander , already an accomplished songwriter decided he couldn't live in the spotlight after the success of their first album so that was the end of the band.

Another couple of great debut albums;

Lloyd Cole and The Commotions - Rattlesnakes

Mink DeVille - Cabretta