Everyone thinks they will be the next big billion dollar company. Ideas are worthless without execution. Part of the equity equation will be based on the founders, their track record and how far along the idea is. Other factors include the market, your timing around fundraising and if you have any traction. Raising on a deck vs. actually having revenue result in very different outcomes. There are no rules when it comes to investing and equity. It's a negotiation.

I am assuming this is a genuine question.

I will be blunt. A ticket in the powerball lottery have a potential to return $500 Million. But the ticket price is at $1 due to the low probability irrespective of the potential. Similarly the probability of seed funding company provide decent return is 5% and the probability of it provides some return is another 5%. 90% of the seed investments lose. There was a paper from David Rose with the accurate numbers from gust platform.

Typically investors take 10-20% in each round of funding.

I don't think it matters whether it will be the next google, Facebook or Amazon. Equity in a company is a direct reflection of value. Always keep in mind that when you hear things 5-15% as a normal amount of equity, that is more of a guide than a fact. Always focus on the value that the party asking for equity will bring. 10years from now when you have a big problem to solve that's when that equity will matter. Essentially who's on your team and what do they bring to the table now and in the future. Ask your self that question. Here is a tool you can use to help you out with it: https://cofounders.gust.com/