Depends on budget. Vegas literally covers everything.
The first time I went I stayed at the LV Hilton (which is no longer a Hilton). It was a typical US chain hotel with the added benefit of a casino (and cheap, about $60 per night). Buffet was ok, but it included wine and beer so we well and truly got our $20 worth! Location was a little far off the strip though.
Last few times I've stayed at the Luxor. It's considered a bit "low end" now, but it's cheap, well located and comfortable (plus has a little LV wow factor).
If you have cash to spend, get an executive room at the Belagio. $250-300 or so a night, but the lounge overlooks the strip from up high and it's great to settle in and watch the strip come alive in the evenings with a coughtail.