I would give Bally's a 3.5 stars. It's an ideal location being right in the middle of the strip and a great deal just based on that. It is attached to Paris and across the street from the Bellagio fountains.
I stayed in an Indigo room which is their basic, non-updated room. It is everything that you need but no frills or fancy decor. The rooms are clean and comfortable. Lower floor, no view (we were facing the monorail and street but could also see the highroller ferris wheel). The staff was friendly. Like many of the other resorts, there is gaming in the lobby and shopping inside & adjacent.
The place won't wow you like staying at the Wynn, but it's much more affordable, clean and in a great location!