There is an entire section of the store called Great on Deck. It shows games tested by valve, but the number of untested games are much larger. You can use protondb.com it has the comunity experience with tips on how to make games more enjoyable such as improving battery life or how to make harder games to run in an acceptable way. Check it out.

Try this page: https://psteamproxy.yuanyoumao.com/greatondeck

i dont own a deck yet (is not available in my region, and im currently not willing to py scalpers, lol), but i have played these in linux. if you occasionally like to play games with unusual gameplay or a bit experimental, this ones are really good imo

stealth game (not a shooter) with platformer + puzzle and "collectaton" mechanics (starts a bit slow, but has an intersting story and unique ambient). unfortunately dev studio disbanded, and they failed to properly promote the game, so its unknown if eventually someone else will pick it up.
https://psteamproxy.yuanyoumao.com/app/551770/ECHO/

puzzle platformer game with golf theme, and some random rogue-like elements. great music
https://psteamproxy.yuanyoumao.com/app/1726120/Cursed_to_Golf/

boss rush with bullet hell and swordplay mechanics. also great music
https://psteamproxy.yuanyoumao.com/app/423230/Furi/

this one is a bit like racing, but with flying mechanics and parkour + obstacle evasion; nice music; also has many tracks made by users in steam workshop
https://psteamproxy.yuanyoumao.com/app/233610/Distance/

not very experimental, but good if you like mario-style platformers; also has a lot of levels and mods that expand a lot the game, and offer other options to play it
https://psteamproxy.yuanyoumao.com/app/253230/A_Hat_in_Time/

this also isnt very experimental, and some may find it frustrating; also until recently it had some issues with the mod manager and a forced launcher which was removed. imo the full version (with all dlcs) is pretty good, and specially thanks to mods that add many monsters and options to modify the appearance of soldiers, or even follow specific themes (ie star wars or resident evil)
https://psteamproxy.yuanyoumao.com/app/268500/XCOM_2/

https://psteamproxy.yuanyoumao.com/app/2754380/The_Roottrees_are_Dead/

https://psteamproxy.yuanyoumao.com/app/835960/The_Talos_Principle_2/

https://psteamproxy.yuanyoumao.com/app/1569580/

https://psteamproxy.yuanyoumao.com/app/2015270/Rotwood?snr=1_25_4__318

Very chill and relaxing 3D platformers that are absolutely stunning to look at on Steam Deck and runs really well on the device.
https://psteamproxy.yuanyoumao.com/app/996580/Spyro_Reignited_Trilogy/

Fun game to play solo or with friends, made even better with proximity voice chat that you can easily take advantage of with the Steam Deck's built-in microphone.
https://psteamproxy.yuanyoumao.com/app/3527290/PEAK/

Fun and addicting farming game that can keep you hooked for hours on end, with lovely pixel art that looks great on the Steam Deck.
https://psteamproxy.yuanyoumao.com/app/413150/Stardew_Valley/

Never played this one before, I liked it a lot and it works great on deck https://psteamproxy.yuanyoumao.com/app/1174180/Red_Dead_Redemption_2/

引用自 ✔：

My deck should be coming in a day or two, so I'm not entirely sure what the best titles are for it. I heard from some other forums that 'Cult of the Lamb' and 'Hades' are great on it. Probably going to get 'Laika: Aged Through Blood' as well. I've personally been more interested in roguelikes and puzzle games lately. Any other suggestions?

The TOMB RAIDER DEFINITIVE SURVIVOR TRILOGY are excellent games and they run perfectly on the deck.

UNCHARTED™: Legacy of Thieves Collection is excellent too. Also runs like a dream on the deck.