Epic doesn't own the stuff on EGS but they still spring for some good titles. Valve has billions of dollars too so this is just them being cheap - especially at a time like this. I hate cheap people. Steam's always pissed me off because it's so half-assed. It reflects that Gabe is a cheap man.
Much like PSN and XBL, companies mostly give away back catalogue and indie stuff on these things. If you're expecting AAA current titles then yeah you're going to be disappointed. Epic has given away more AA and a few AAA titles in the past year because they're trying to get a stake in the industry. Valve has a stake and a fully featured client so they probably don't feel the need to buy your fleeting favor.
Personally I thought Into The Breach and Subnautica were really the standouts from their giveaway. The Arkham Trilogy was solid but pretty old at this point. Stuff like World War Z and Just Cause 4 is "ehhh its free but I probably wont actually play it" type redemptions. In fact I think on most of my "freebies" across the various services I probably play 10% of them. Too much current stuff to ever catch up on that back log!
Playing: Xenoblade Chronicles DE, Ys IX, God of War
Watching: Lupin, You me and the Apocalypse, Days of Thunder