If you head over to myaccount.google.com/dashboard, you'll find there's a listing for the Play Store on this repository of your various Google account stats. The figure is "installed apps," which is the number of apps Google knows you have installed on devices over your entire account history.
It's an interesting figure to compare: how many apps does Google say you've installed and kept on your various devices over the years? I'm guessing my history as a phone reviewer has slightly... skewed my results.
Then again, I don't try many new apps in the first place, so maybe you've all got me beat! What's your number? Indicate where in the range you are in the poll below, and discuss in the comments section. (I did my best to guess probably ranges here, as I'm working with a data set of one at the moment.)