Great dining is a mix of great food and a great time. The steaks at Le Cellier are good, and I really enjoy eating there, but some of that is nostalgia - it is the first place I dined on property on my first trip.
I have had positively atrocious food at Coral Reef each of the four times I've tried to dine there. I might just be "lucky" but I cannot recommend it for a meal which has so much at, er, stake. By horrible I mean improperly or undercooked fish and seafood, sloppily plated dishes that were missing key elements, and excessively salted dishes. The last time I dined there was in Dec '06, so they may have had a rebound since then.
The best steak I have had on property was at Narcossee's. It's also about the most expensive. Coming in a close second was Yachtsman, which might have gotten better marks if the dining experience was more to my style. Narcoosee's is a little more informal, and you can see the MK fireworks from the restaurant or its veranda. Shula's delivers a superb steak and provides an opportunity to dine in a non-Disney restaurant without leaving property. It is also a very expensive restaurant.
The best beef served at Epcot is not a steak, although I have had nice steaks at both Le Cellier and Chefs de France. The best beef is short ribs of beef at Chefs de France. It is a memorable dish. Simple, delicious, and wonderfully beefy. If you are looking for a home run at Epcot for a beef lover, I'd steer them in that direction.