What is the easiest and cheapest way to create a website like Youtube?
for example, a website where users have the ability to submit their
own videos, with rating system for each video etc.

This won't be much of an answer, but it's going to cost A LOT.  The
bandwidth, alone, required to allow users to constantly upload and
view videos is MASSIVE, and will run you in the thousands of dollars
per month, even without much traffic.

Not to mention the programming of the site.  Unless you expect users
to be able to encode their own videos to a web-friendly format like
flash, you're going to need somebody to write a proprietary video
encoder/viewer, which will also cost several thousand dollars.

You could, instead, just allow users to upload various video formats,
which any talented PHP developer could help you setup for probably
under $1000 (check guru.com for developers).

Keep in mind that at this point YouTube (as far as I know) is barely
breaking even on their bandwidth bill (which was $1 million/month,
last I heard), and not turning much of a profit.

You can buy the YouTube software already packaged and ready to go.

If you search it enough you can find it.