Backlog is sitting at 28 games right now. Not ideal, but not too bad. Back in 2014 or so it was still around 150+ or so. I only really buy games I fully intend to play anymore. As for stuff like bundles, I just keep what I actually want, the rest I give away. Don't need that shit clogging up my library. Also helps that I imposed a "no impulse buys" rule and a strict monthly budget.
That's games I buy tho. Free games? Yeah no, bit more dramatic of a situation. 300+ games probably? Lemme see, every Epic Store giveaway ever, that's probably close to 150-200 already. Another 50-80 on GOG. 20-40 on other launchers like Uplay and Origin and such, which I never use. Like 10-15 digital games for PS4 and Xbone, neither console I actually own. Could be more. Could be less. I have no clue, stopped tracking them a couple years ago, just write the ones I might just play one day if I'm every done with my real backlog down in a list. Only time I pay it any mind is when I ctrl-f to see if I hadn't gotten a game I want to buy for free at one time.