Both RE4 and DMC3 have perfectly paced boss encounters. DMC3 is not more than 1 per mission and if you consider RE4 to have the Lake Monster, El Gigante, the Village Chief, Salazar, It, and Krauser (you could even throw in Saddler but whatever), it's still like 1 boss every 2 hours and the average is way skewed at the end of the game. GoW2 has too many bosses for its length...the bosses don't get that build up.
And nobody except action game nuts delve into what you're talking about with the satisfaction of bosses based on mechanics. A random sample of gamers would probably have the Colossus as people's favorite GoW2 boss (a QTE) and the Hydra as their favorite GoW1 boss (not a QTE but fairly repetitive). I think the sense of accomplishment is diminished when you only play 20 minutes in between bosses.
I think Sony's "official" listing of bosses is like 14. I think there's legitimately about 8.