/vr/ - Retro Games

A few people recommend playing Sonic at some point, and I'd agree. Sonic 3 is especially short and gives you an "easy mode" by letting you fly as Tails. (Not technically retro, but Sonic Mania also does something similar, and can be a bit more forgiving in places.)
But something to keep in mind: Sonic has a few arcade sensibilities. Sonic 1/2 have no saving, sometimes you need quick reactions to enemy placement, getting all the emeralds is hard and there are multiple routes so it encourages replays. Most big-name platformers in the years following will lean a litle closer to Mario in their structure. So if you try Sonic and find some bits aren't to your liking, don't let it put you off platformers.

The Kirby games are also tailor-made for beginners, while still usually having an enjoyable difficulty curve. Kirby's Dream Land on GB is very easy; and Kirby Super Star has an even easier, shortened remake of it with better graphics as a "first world". Adventure is also

>>9551193
https://www.mariowiki.com/Super_Mario_All-Stars has a list of all of them.

In all of them, the biggest changes are graphics/music, and the ability to save after each world.
Super Mario Bros. 3 gives you a few extra lives to start off, some very minor layout changes, and it lets you run and throw fireballs at the same time.
The Lost Levels has some more extensive changes to make it easier (saves after every level, extra lives on World 9, making access to worlds A-D easier), but it's still the hardest and cheapest game in the collection (and I think the Mario series as a whole).