I think Dews is spot on. Just comp titles and what makes your book stand out should be good. If a book is super duper successful, chances are, they've heard of it. If it has loads of reviews on Amazon, it's probably well-known/successful. If it's by a big author or illustrator, chances are also good that they've heard of it. You can also look at the editorial reviews listed on Amazon. If there are a lot of glowing reviews or stars from major reviewers (Kirkus, PW, SLJ, etc.) then it can be considered successful.
(Also, just want to note, I've never actually been asked for a market analysis.)