The first year of Superman....any of the DC Archives Plastic Man volumes...any of the Eisner Spirit volumes...Simon and Kirby's Captain America...the first two years or so of Submariner in Marvel Mystery. These are probably the strips that would resonate best with a modern reader trying to find good early comics that don't seem too alien.

Supermen! is great but more geared toward obscurities. I really love the Hanks books but they are not for everyone. I also really like Captain Marvel and other early Fawcetts but those stories and characters seem to miss a lot of folks today.

After about 1945, there are a LOT of high quality comic books, more of them available in gorgeous reprint editions every day....