I love platformers. For 2d, I usually prefer action platformers over pure platforming. So, let's see what comes to mind.

You gamers HAVE to play Sheepy: A Short Adventure. It's free and has an exceptional atmosphere.

I started with what I had fond memories of and came to mind, but of course, I went to my steam library, and looked through games tagged platformer. And now I'm wondering if I should also link my reviews of the titles, specifically the most interesting ones. Either way, the list of fond memories / very positives became too long for one list, so it's split by category now.

3d ego platformers

• A Story About My Uncle, left a lasting impact on me back then as a very good if not exceptional title
• Portal
• Hot Lava, great, pure 3d platformer, a lot of of quality content
• Supraland, 3d puzzle and action platformer

3d 3rd-person platformers

• New Super Lucky's Tale, a great 3d platformer
• A Hat in Time, a great 3d platformer, with cute characters, good humor
• RiME, I remember I wrote a very positive review about RiME
• A Short Hike, great
• Yooka-Laylee

2d platformers

• Sheepy: A Short Adventure, free, exceptional atmosphere
• Ori, with its great atmosphere and visuals
• Webbed, very cute, great theming, playing as a spider
• Yoku's Island Express, great mixing of pinball and platformer, in a great setting
• Spiritfarer, great atmosphere
• Battleblock Theater, great absurd humor
• Super Meat Boy, ok, this has been a long time ago, but it was incredibly fluid and fast, with a ton of content
• Dustforce DX
• Jubilee, I played this on my Steam Deck quite a bit (unfortunately no save sync)
• Trine, for its great physics approach and narrated humorous storytelling
• Wunderling DX, an "auto-runner platformer", quite interesting, well polished, so try to for something different
• Braid, I don't actually know if it holds up today, it's been so long ago

I'd love to hear your opinions on

• A Highland Song, deep lore, great atmosphere - I felt a bit lost though, or wasn't captivated beyond that, and beyond one run
• Treasures of Aegean, another "roguelite" platformer, with interesting progression and discovery - still, I found it well made, but ultimately not personally captivating, maybe because of the disorganized nature [of re-runs and timeloop-crossing story]
• Sable, only partially platformer, and not the best quality overall, but great atmosphere, exploration, and platforming discovery
• Verlet Swing
• Viking Hiking
• Grow Home