There's also Amplenotewill it ever end
Not for a couple of years I think.
To be fair to Amplenote, they've been going since last year, so predating Roam's popularity.
Most older apps will be looking to add similar functionality, without necessarily understanding how it would be used, and the new wave will be adding features.
My recommendation for users is to make a decision about database or files (or any combination according to preferred workflow), pick the app(s) that seem to suit best for now and then just use it(them). Check alternatives only when hitting an issue. They're all going to change and develop dramatically (some will vanish) and it will be easier to compare in a few years. Everyone is aware of what the others are doing, so the whole herd will add desirable features in a lagged sync.
Wiki-links have become standard. I expect that there will be a lot of pressure for markdown expansions to cover the new usage. I've already seen proposals to replace markdown completely. The new generation of users won't want to be adding HTML for simple features like underlining or colour.
I've noticed a huge proportion of Mac users on Obsidian boards - Linux too - and believe this is also true for Roam. Obsidian's developers use Windows. Not sure if this has any implications.
Also noticed that Dendron now has transclusions; not sure when it was added. I expect transclusion to be as pervasive as bidirectional links. I can see that having a big impact for Notion in particular.