The very best?
Men of War series of WWII/Cold War tactics.
Cossacks strategies, the first is the pinnacle, subsequent games aren't even half as good, but also worth a purchase if you like historical strategies (and might be worth it to check their American Conquest and Heroes of Annihilated Empires as well).
S.T.A.L.K.E.R. from the same studio that brought us Cossacks, and
Metro are great post-apocalyptic survival shooter series.
Frogwares' Sherlock Holmes and other adventure games are pretty decent.
Of the rest, Collapse was critically panned for being a crude DMC knock-off, but I don't regret buying it (deluxe metal case, even), and neither I do regret buying You Are Empty, which also was objectively bad game that I liked a lot for some reason (aesthetics?).
LootHunter: Actually, you should check again. They are based in Poland as of late and recently were bought by Tencent.
I don't think it makes things any better for people who care about that sort of stuff, especially since Tencent owns them whole, as opposed to mere 40% they have in Epic. They also have been known in the past for more reproach-worthy things like draconian (and buggy to the point of making games unplayable) DRM, unsavoury business practices and occasionally not paying developers when they could get away with it. And really shitty code when it came to their own products.
But they also published some great games that I'm not sure would've ever seen the light of the day otherwise, helped development teams in Russia, Ukraine and altogether outside of former eastern block to find their feet and lately they bring us some interesting pseudo-indies with a retro feel. And they release their games on GOG, DRM-free and stable for the most part, which more than makes up for their past transgressions, I reckon.