There are two graveyard/late-night buffets: at the Riviera and the Boardwalk. The Riviera late-night buffet is open Saturday through Thursday nights (it closes at 10 pm on Friday night and reopens at 6 am on Saturday). The Boardwalk buffet is open 24/7
Now the question becomes: Are they decent? That's a matter of taste. Try them both and let us know what you think.