Honestly, with Proton, the answer is "many of them", so it all depends on your personal taste!

My current highest Steam counter goes to Stellaris, the Paradox 4X space strategy title.

For me "best game on Linux" basically just means "best game" since everything I play runs perfect of very close to perfect.

That means Terraria is the winner for me. Best game of all time IMO, and it has a native Linux port that works great.

Night in the Woods. A story based game with cute art and amazing characters.

@IndependentRanger too many to list, but my money goes to RimWorld, No Man's Sky (via Proton), Stardew Valley, TMNT Shredder's Revenge, Axiom Verge, Hollow Knight, Starbound, Valheim, VVVVVV, VirtuaVerse, Celeste, Undertale, Crosscode, Crypt of the NecroDancer, Dead Cells, Jupiter Hell, and a few other games that escape me at the moment.

I'm assuming you're talking about native Linux games?

If so, KPatience. lol

Morrowind (via OpenMW) is a classic. I've put in quite a few hours into Terraria as well. Through Lutris/Wine, I've also been enjoying the classic infinity engine games (Baldur's Gate, Icewind Dale, etc).

Stardew Valley

Thanks for the suggestions! Very new to Linux gaming and wanted to the recommended games. The Steam summer sale is almost here and wanted to be ready.

Factorio is pretty fun

Most games run in Linux these days. It's especially easy if you have your game in steam and enable proton in settings. As for a favourite. That's hard to say. I have accumulated so many games over the years, I can't name a favourite. I played a lot of overwatch before they messed it up with the f2p patch. Otherwise, I've been playing some rimworld lately and some don't starve together. Edit: It just struck me. Underrail is a game I could count to my all time favorites.

My top 3 are:

1. Slay the Spire
2. Celeste
3. Into the Breach

2D indie games, that will run pretty well on a laptop with no dedicated graphics card.

Oxenfree and Hollow Knight are two of my favourite “current” games. Can’t wait for Oxenfree 2: Lost Signals to come out in a month or so…

Though Oblivion, Skyrim, and Borderlands 2 might be the ones with the most playtime.

Nethack variants like Unnethack, Slash’EM and Dynahack are a perennial favourite on any OS since Hack on MS-DOS in the 80s and Nethack on the Amiga in the 90s.

• super tux cart
  • ... I actually was surprised by the maps with cool shortcuts
  • nice singleplayer experience, if you just want to chill while listening to some of your music offline
• Zero-K in case you miss supreme commander / like managing a robot army
  • some robots are cheap and expandable, some are expensive and have special abilities that require micromanagement.
  • I personally play in skirmish mode against bots
• 0AD if you like micro manage your own RTS population
• minetest
  • minceclone2 "subgame" to get somewhat interesting mobs
  • I wrote some mods for it myself in lua, adding static blocks is way easier than adding any kind of ~~intelligent~~ mob

My current game rotation:

Guild Wars 2, Dead Cells, The Binding of Issac and Civilization 5

Two native and two via Proton, it is amazing as a non-programmer how good Proton is. They run like native and rarely have to fuss with anything. I might be lucky with that but Linux gaming has really covered a ton of ground in a pretty short time frame.