Yes, Mom and I regularly split meals when we go to WDW together and have done this at the Sci Fi. I believe the burgers are 1/2 lb uncooked, so, they're pretty big, and they're served on a big roll - good too. We usually split the burger and fries, and I get a milkshake with it. Yum.
Sharing meals is a great way to save money too, plus if you're still hungry, you can try more things - especially at Epcot.