Totally.
Also in agreement on the Gorillaz thing. Their self-titled album took a bit to grow on to me, but Demon Days was just an immediate hit.
Wheatus is another good example. Their first album was okay, but was also lacking in a lot of areas. With Suck Fony and Too Soon Monsoon, however, they really improved in their songwriting, making a lot more cohesive and interesting songs.
Thrice should be mentioned, too. Artist in the Ambulance was at best catchy and at worst too screamy. They came back with Vheissu, though, and showed a lot of talent, exploring all kinds of sounds.
The last one I can think of is Brand New. Your Favorite Weapon was pretty bland (the band themselves even admitted to this), but man, they struck back big time with Deja Entendu. The difference in quality between the two albums is amazing.