Well you have an immense amount of choices in Las Vegas.
If you want to go with the traditional steak house, you have (my top 10 ranked in descending order of preference)
Prime (great steaks in a french style)
Morton's (I recently reviewed them in RR)
The Steakhouse at Circus Circus (still great)
Delmonico's (tender steaks)
Smith and Wollensky's (just like NY)
3950 (good but I had a better steak at Red Square in MB)
SW Steakhouse (I ate there when they were pretty new, they've probably moved up a bit by then)
Lawry's (more prime rib, but still good)
Rosewood Grille (good steaks, better seafood)
The Steakhouse at Camelot (pretty good KC strip)
The Steakhouse at Luxor (filet was just OK)
If you want to go with a more full menu restaurant consider: (again top ten in descending order)
Bradley Ogden (IMO best restuarant in Vegas)
Tableau (very nice in the FL manner)
Lutece (underrated)
Le Cirque (good food, if a bit stuffy)
Aureole (I like CP, some people don't)
Mix (AD, but not as good as his other offerings)
RM Seafood (pricey, but good)
Picasso (underwhelming, but still a good restaurant)
Olives (If you like this chain...)
Commander's Palace (very nice)
For ethnic food, there are a number of offerings, but I'm not sure which of them would be appropriate for a business dinner.
Hope this helps, feel free to ask if you'd like more information about any specific restaurant on my lists, I used to spend about a month out of each year on the convention circuit in Vegas so I know the restaurant scene quite well.