A Google search will generally turn up sites like Siftery, among others ('A vs B' is one of our very top organic search traffic drivers).

Hope you'll take a look at the substitutes data specifically though. We're showing companies that are actually switching from one product to another, and then rolling that up to showcase some trends and insights.

I have been going to Crunchbase, looking up a company, and scrolling down to see their "competitors." Though, they're often not listed.

But, I like your suggestion and will give it a try in the future.

except how do you think google mines that data. if those sites go away so does google's free loading....

Google mines that data by other people searching for that, not (only) by scraping it off sites. Yes, they also do that, but AFAIK search trends have a higher relevance than scraped suggestions.

As long as people want to know how their existing product stacks up against another product they have heard of before, "<existing product> vs <other products>", will be searched and appear in the autocomplete.

This approach breaks down tough for newer products, ot if you want to find the best product by quality, not just popularity.