The very best steak is at Shula's, over at the Dolphin. It's not a Disney restaurant per se, so the service is more "correct" than Disney friendly.
Yachtsman Steakhouse steaks are a bit below those at Shula's, but still good nonetheless.
Other steakhouses include Concourse steakhouse, Le Cellier, and the Maya Grill. And other restaurants have a good steak as one of the entrees'--Jiko and Flying Fish come to mind.
But if it's just the meat--Shula's.