It's a good question but it becomes a more useful question with a few specifics worked out;
1. There's way more normal play when the wheels are turned a little bit. The steering box is built so that the tightest tolerances are experienced in the dead-ahead position.
2. If you can isolate the play in the steering into any of the components;
a.
There shouldn't be much play at all in the tie rod balls, the the wheel bearings, the place where the steering box bolts to the subframe, anything under the car.....
b. There might be an inch or more of play in the steering box itself and that's probably ok. There is bound to be a little play always.
c. There might be a little play in the u-joints on the steering column or the telescoping part of the steering column and that's probably ok.
Here's a more direct answer: With the car off and the hydraulics not pumping I have gotten my steering wheel down to about 3/4" of play after considerable tinkering. That would probably measure as one inch of play (2.5cm) if I still had my big, original (400mm) steering wheel to measure on. And I'd be
super interested if someone else claims they've done better!