Content is King for a search engine spider (but links can rule for rankings - regardless of the content) - meta tags are pretty much ignored for ranking purposes (though the description tag can be useful and should be there for each page), the keyword tag is a load of hot wishful thinking and the title tag (which is very useful) is not (strictly speaking) a meta tag.

Thanks. Which means, Title Tag is a must. Right?

The title tag is a critical component of "content". The keyword meta tag is essentially deprecated. Though it is "useful" for providing information for your competition. ;-)

The meta description is a valuable tag but for SERP click-through rather than rankings.

I enjoy taking liberties with Occam's Razor so here goes: Within two sites, all SEO factors being equal including content, the site with the better title tag is preferable.