I liked Bellagio's buffet! This is the second buffet I went to during my trip and the food variety was great :) Items that stood out to me were the king crab legs, marinated cod fish and prime rib.
Service was excellent. Our server was always available and she checked in with us in good intervals.
If you're going for Cirque du Soleil's "O" show the same night, make sure you head here early because the lines were already building up at around 4pm.