Three new games added to list (post 1),
Subnautica,
Conan Exiles and
Dark and Light, all three are
prerelease games. Dark and Light released just last month, all are survival, sandbox games. I'm not sure about Subnautica, but Conan and D&L both feature solo/multiplayer, offline/online, PVP/PVE, both private and public servers, not MMOs, server sizes run in the range of 30-100 players. As with
Ark: Survival Evolved,
Conan, and,
Dark and Light run on the Unreal 4 engine.
Note: Photobucket seems to be messing with the ability to post image links back to their service without paying a $400 a year subscription. If you see a warning attached to any of my images, just ignore them.

If any of the images are not appearing for you, please comment. One of the Conan images is uploaded from my computer. Guess I'll be looking for another free online service...
NPC- A non-player character (NPC), sometimes known as a non-person character or non-playable character, in a game is any character that is not controlled by a player. In video games, this usually means a character controlled by the computer through artificial intelligence.
Comparisons of 3 Titles:
ARK: Survival Evolved- (
Dedicated Thread) The oldest of the three and still in prerelease status. Recently the purchase price was hiked substantially. (The advantage of buying early pre-release.

)
Survival, build, fight and tame dinosaurs. Dinos are ARK's bread and butter. The original setting is a deserted island, but the game includes multiple maps including procedurally generated maps. You wake up on the beach in your undies and start scrambling to survive. You can be dead in 30 seconds.

Characters creation is somewhat limited although you can create toons with bizarre shapes. The primary attraction is a beautiful environment filled with a huge assortment of passive and dangerously aggressive dinosaurs. There are caves and off shore underwater environments to explore. There are no NPCs, except for dinos. No lore or questing structure to date.
Conan Exiles- (
Dedicated Thread) Survive, gather, build, capture human slaves to do your bidding, fight and kill critters. Captured thralls (your slaves) are put on a wheel of pain to break them.)
A criminal left to die in the Exiled Lands, a mysterious stranger frees you from your cross. Follow the road to the river, start feeding, clothing, building and arming yourself against the many hazards, including both animals and local human NPC tribes people.
The Setting is the Conan Universe, initial prerelease was Jan 2017, featuring an arid landscape although there are 3 biomes included. Primarily desert, there are two smaller areas designated prairie and savanna. Although I prefer the jungles of ARK, and you may not prefer rocks to the horizon, of these 3 titles, Conan has the prettiest environment as far as graphical rendering, artwork, everything is beautiful. Recently added a dungeon, there is some lore (with more to come), but no questing structure to date. Arguably has the strongest building abilities of the 3 titles although in a recent patch, the developer nerfed the ability to build in deep water (bastards!). I think this was to promote PVP (player vs player) and the NPC raid feature that is planned.
Conan also has nudity, none, partial or full depending on what setting you choose. If you don't like seeing bouncing boobies and wangers, turn it off. On a multiplayer server, this is an individual choice and does not hinder others from selecting it. You just won't see it if it's turned off. It's incorporation into the game seems natural for the setting. You have been left naked to die on a cross, but to survive, you will cloth yourself.
Conan Exiles
Dark and Light- As of this writing only a week old, survive, gather, arm, build. Some have described this as ARK with NPC vendors and merchants, including animals which can be tamed and like ARK, have gathering specialties. The first biome is a pleasant forest/alpine area with 3 faction towns to start in, human, dwarf, and elf. If the size of the map shown on the launch screen comes to fruition, it promises to be a very large world.
The graphics look very similar to ARK. It's new, but imo has the weakest building as far as flexibility and choices. The taming mechanic is a variation of the ARK method, knock them out, then feed them so they will become your buddy. There are a variety of fantasy and prehistoric creatures, like goblins, ents, unicorns, and... dinosaurs. As of this writing no lore or quests, although you will be guided on how to progress, if you want to call those quests.
Dark and Light (suspiciously ARK like)
Conclusion- All of these games are variations on the same theme sandbox survival. There are no formalized questing structures like a typical MMORPG, no story, and minimal lore if any. The structure is freedom to explore, build, raise skills and stats, and tame animals or slaves that assist in this endeavor. All 3 have both PVP and PVE settings. I've observed that exploration is fun, but it only takes me so far. The attraction of the game is after I've seen the sights, what do I do now?
All titles are repetitive and grindy. Just how many hours do you want to spend chopping trees and rocks?

A lot depends on your tolerance for such activity. If you have a low tolerance for grind, but enjoy building or taming/enslaving

a godsend is the ability to play these games in a solo/private server creative mode by using the game's console to give you what ever you want, and take on whatever challenges that you enjoy. For example, in Conan, I build creatively, but I engage in combat and capturing slaves like the game intended.