Either Alan Davis and Mark Farmer or Frank Robbins and Frank Springer.

Kirby and Colletta

Colan / Palmer

We did this as a Classic Comics Christmas topic back in the CBR days. My #1 pick was the team of Ross Andru and Bill Everett, specifically their work on the Defenders origin in Marvel Feature #1.

Cei-U!
Pretty sure Severin & Severin was my #2!

Yes we did.  And if my answer wasn't Don Newton and Alfredo Alcala it probably should have been.  

Speaking of Alfredo Alcala...Mark Evanier tells a story about how prolific he could be.  

Alcala's transition to drawing for the American market began in the early seventies when an intermediary arranged for a group of artists in the Philippines to sell work to DC Comics. Alfredo often told the tale of going to a hotel in Manila to show his samples to Joe Orlando, one of DC's senior editors.

Orlando was naturally impressed with the quality of the work he was shown. He told Alfredo that DC would hire him and asked how many pages per week he could produce.

"Forty," said Alfredo.

The editor was startled. The least exhaustible DC artist would be hard-pressed to pencil and ink ten pages in a week. Then he realized that Alfredo probably assumed he would only pencil or only ink. "No, no," Orlando said. "We want you to do all the art...pencil, ink, even lettering."

"I see," Alfredo muttered. "I pencil, I ink, I letter?"

"Yes," Orlando nodded. "Now, how many pages per week do you think you can do?"

"Forty," said Alfredo.

Again, the editor was startled. Obviously, there was some sort of misunderstanding here. He figured that the artist before him was thinking in terms of very simple pages with only two or three panels on each and no detail. Fortunately, Orlando had brought along with him, several dozen pages of original art from past DC books. He showed Alfredo pages by Neal Adams, Joe Kubert, Curt Swan and others.

"We want work like this...these many panels per page, and this detailed," Orlando explained.

"Oh," Alfredo nodded. "You want me to pencil, ink and letter pages like this?"

"Yes."

"Well," Alfredo explained. "That changes things."

"I would think so," Orlando sniffed. "Now then...how many pages a week do you think you can do?"

"Eighty," said Alfredo.

Skeptical and disbelieving, Orlando put Alfredo down for 40 pages per week. Soon after, when Alcala pages began arriving at DC at that rate, it was assumed by some that "Alfredo P. Alcala" was the joint moniker of perhaps a half-dozen hands. Not so — as anyone who later saw Alfredo sketching at a convention can attest.

The guy made pretty much every other artist look like a snail. 

Don Newton/Kurt Shaffenberger