Quoted from RipleYYY:lots of other games should be in than, as just for example Metallica...
He is citing people who have done voices / callouts for multiple games.. Quite a few for Kitzrow.. and 3x for arnold.. both very memorable and important for their respective titles.
Agree if you need to set some threshold, but I am pretty sure the two examples are featured on at least 3 machines.. so that's probably a good start.