You ever handicap a horse race?
Think of Google search as your racing sheet.
- take each TLDs years of existence
- assume the time that domains are developed in -- this is a wide assumption. This also affects the TLD extension's brand value to some degree -- less every day IMO
- factor the length of the domain name and or its semantics.
Take 100 SERPs listed for the same keyword.
70 -80% on the names will be .com but I think you need to understand the reason -- the reasons have little to do with the TLD itself.