Oh brilliant.
I had a really nice and long reply typed up, but the ****ING DATABASE SERVER EATED IT.
Re-hash follows:
There are many factors affecting how loud a song appears to be, and the Sound Check can only address what is arguably the LEAST important criterion: the maximum level in the song.
It says nothing about the AVERAGE level of the song (an Jack Johnson album of just guitar and vocals will be mastered to the exact same maximum peak level of -0 dB as Ravel's "Bolero", which starts of with a pianissimo snare and oboe, and climaxes with a full 60-piece orchestra playing forte fortissimo. At the same volume setting, you WILL strain to hear the snare), nor does it say anything about the actual LOUDNESS of the song.
Newer productions will tend to be heavily dynamically compressed, making them sound louder and "thicker" (and also much more tiring to the ear), but also destroying the natural dynamics that make music interesting (and often enough these days, literally destroying the sound of the music itself by over-compression). You'll find that on newer productions (and also on the dreaded "remastered" versions of old recordings), often, the guitar intro will be just as loud as the final chorus, with full band, four guitars, backing vocals, and 40-piece string orchestra. This is obviously not natural, but results in a much higher perceived loudness of the entire production, especially in direct comparison with better-produced/older/classical/jazz recordings.
There is nothing you can do - and certainly no automated mechanism - to counteract this except listen to music the way it was intended: as a full album. Albums are usually produced to a unified sound, so you won't need to touch the volume dial until you put on the next album.