For my part, I haven't gotten anything new yet, so if you've read my recommendations before, I apologize for any repeats. Roguelike Edition, apparently.
PlateUp! is my favorite couch coop game on Steam. You and up to three friends work together to run a restaurant. It's a little like Overcooked, but instead of having different wacky levels to get through, you choose a menu (starting with one dish), and build up your restaurant day after day. Every few days you will have to choose a new complication (like another dish or reduced customer patience). The goal is to get through 15 days of service without a single dissatisfied customer, so it's like a restaurant roguelike. It's currently 70% off and 94% Positive all time.
Dead Cells is a very fun sidescrolling roguelike that feels a bit like a Metroidvania. Collect weapons, kill monsters, die, repeat. It's currently 50% off and Overwhelmingly Positive all time.
FTL: Faster Than Light is a classic roguelike at this point. You must traverse the different sectors of the galaxy to reach and destroy the Rebel Flagship. You can order crew members around in real time, while the ship weapons take time to recharge, giving a turn-based feel. It's 70% off and Overwhelmingly Positive all time.
Noita is an amazing roguelike as well. You play a wizard attempting to explore down into the earth for treasure. Every pixel in the game is made out of a material, from plain old Dirt to flammable Oil to useful Water. Find treasure and new magic wands. Mix and match the spells on your wands to make new effects -- and even utterly broken bullshit. It's 60% off and Overwhelmingly Positive all time.
What about you? What do you recommend?
FTL and Noita are two games I highly recommend. Both are fun as-is, but FTL in particular has some mods that soften the difficulty curve a bit and vastly increase replayability.
What I'm looking at buying at the moment is the Star Control series, Fallen Enchantress, Mindustry, and the Crash Bandicoot trilogy. I might grab some of the Galactic Civilizations games, but based on the reviews I might enjoy other space 4x games more.
I also bought Master of Orion I & II on GoG (need to check if a couple of the above games are comparably priced there) because they were more or les the same price, and GoG tends to do better on making old games work on modern hardware, along with allowing you to download DRM free versions.