I believe The Beatles: Rock Band came the closest to being perfect. Eveything about that game was just beautifully done and the only things missing was Pro Drums, an option for Keys, and a few more Beatle songs (Hey Jude, Strawberry Fields Forever, Yesterday etc. etc.)
I respect this, but always had trouble with portal 2. It has some great parts but is also way too long.
It is definitely a bit longer then it absolutely needs to be. I personally think it paces itself well, but I can see your point as well.