Not buffets but you could try Art's Deli, Hugo's (big breakfast menu) or Du Par's (good pancakes) all in Studio City area,
Art's Delicatessen & Resturant
12224 Ventura Blvd, Studio City, CA 91604
12851 Riverside Dr, North Hollywood, CA 91607
12036 Ventura Blvd, Studio City, CA 91604
The best breakfast buffet I've been to is the Sunday brunch at Scarpetta at the Montage Beverly Hills. Quality is top notch - everything is cooked in small batches and is constantly refreshed. They have typical breakfast stuff, but also cold seafood, fresh pasta, a carving station, and an amazing cheese table from Beverly Hills Cheese. It's $58/person, so more of a special occasion place, but it's the best representation of a Vegas-style buffet in the area.
I've also heard they do a brunch buffet at the Universal Hilton, but I haven't been.
Hilton Universal BREAKFAST AND OMELET BUFFET
Adults ~ $22 Children (3-10) ~$ 9
Featuring a selection of Fresh Fruits, Eggs, Bacon, Sausage, Potatoes, Corned Beef Hash
Hot and Cold Cereals, Assorted Yogurts and Dairy Smoothies, Gourmet Cheeses, Deli Meats, Smoked Salmon, Asian Delicacies Rice Soup, Freshly Baked Breads and Breakfast Pastries, Fresh Juice. Food is just ok. Not like the mammoth Las Vegas buffets.
Highly recommend the Brunch at Scarpetta Beverly Hills.
Cafe Sierra at Hilton Universal City
555 Universal Terrace Parkway, Universal City, CA 91608-1001
Scarpetta Beverly Hills
225 North Canon Drive, Beverly Hills, CA 90210