Fatburger's been around Vegas for a while and had a reputation as the best burger in town for years. Recently they've been outclassed by SmashBurger and I can say there's not much reason to go back. The burgers are average and served with relish and lots of mayo which makes for an odd sweet taste. Fries taste about the same as those from the frozen section of the grocery store and are rather limp.
This location had particularly bad service. Went in around 8 pm on a weeknight and there was only one staff member behind the counter, trying to fix a broken milkshake machine. Took about five minutes for other staff members to show up and even then they hung around the kitchen area. We had to wait for the first staff member to finish making milkshakes to help us and then he was incredibly unfriendly. On top of that there's no drive-thru.
If you're looking for a good burger in Vegas go to SmashBurger, or at the least In-N-Out. Avoid Fatburger.