Which game should I buy?

Overwatch

H1Z1 is in the next humble bundle monthly, so you could get it for 12$ with some extras.

One is a great and fun classic shooter that grabs the old-school action-packed gameplay of you against hordes of brutal enemies in an ever-escalating crescendo of violent fun. Plus it also has a multiplayer, but it was so not interesting and people neglected it so much that even the greediest most scumbag publisher in the Western hemisphere just gave up and let the devs give all the MP DLC on everyone's account for free as they gave up building any kind of multiplayer scene there.

The other is a dime-a-dozen endless beta multiplayer-only mess that tries to balance its dwindling and gradually dissatisfied player base by offering itself for 12 bucks in the current Humble monthly, where they also throw in at least another four games for free, just so people will buy it and the player numbers do not drop to nothingness.

If you want SP, therefore go to Doom 4.
If you want a multiplayer clusterfuck, then go for… honestly, any random endless beta you wish. H1Z1, ISOLOVETOWRITEMYNAMEINCAPS's MicroTransactions, PayZ, RU$T, whichever blatant scam you are in fancy for.

Never, never, NEVER buy H1Z1, NEVER. Download & play Fortnite Battle Royale for free instead.

The new DOOM, for sure.

I'd buy H1Z1 from the humble monthly xD (betting to get a couple of nice extra games there :D)

Thanks for comments, you helped me very much :)

buy DOOM, save for pubg if you want a fun battle royale game

Easy choice for me since I do not like massively multiplayer games, especially of the eternal early-access kind. So for me it would be Doom :)