When searching for restaurants that I know of, I find the Grubhub/Yelp websites appear well before the actual restaurant's website. I dont know if Yelp does this, but Grubhub has the insidious practice of creating fake websites for restaurants without ever requesting permission to do so.
It's actually Google and Bing that are winning. Everyone else is losing to various degrees.
"SEO" depends on a wide array of factors, such as mobile-friendliness and a semantic link structure. But what ultimately ends up winning are established domains with tons of indexable pages. Backlinks matter, but the difference is negligible for sites that operate on the scale of Yelp.
If an aggregator's page appears before yours on the organic search results, your only choice is to pay Google or Bing to put your listing at the top.
If you are a random restaurant, your 3-page website is never going to beat Yelp.
When searching for restaurants that I know of, I find the Grubhub/Yelp websites appear well before the actual restaurant's website. I dont know if Yelp does this, but Grubhub has the insidious practice of creating fake websites for restaurants without ever requesting permission to do so.