Don't forget that Starcraft 1 had 3 full campaigns. Brood War was a true expansion with 3 more campaigns.
Okay this always kind of bothers me. It depends so much on what you consider a "full campaign".
StarCraft 1 has three medium sized campaigns, with each one focused on a certain race. At most each race has 10 missions each, equaling 30 missions total.
StarCraft 2 WoL had one long campaign, but it focused pretty much entirely on the Terran with some Protoss sprinkled in for good measure. All in all, the whole campaign had 30 missions and dozens of cutscenes sprinkled between them. I would call that a full campaign.
Personally, I loved the focus SC2 had on characters, it allowed me to get to know them better, rather then having to introduce a whole new set of racial heroes in the first two missions of the race campaign while all the others fall off the map. Remember how Raynor only appear twice after the Terran Campaign? Remember how Kerrigan just entirely disappeared and didn't do anything in the final battle?
Really, I think what is killing SC2 when it comes to release speed is the extra focus on character cutscenes and action. It was a lot easier to throw together a dozen missions when all you had to do was have a sprite on the screen and a little "monitor" with a face going "wah wah wah wah wah".
Now they have to make all the crap that is in this trailer, 75% of which is all using the in-game engine.