Shonen is just Japanese for "boy", vs. Shoujo which is Japanese for "girl" (and bishoujo for women, etc.) Shonen is meant for young boys, shoujo is meant for young girls, etc etc. (so the former focuses more on action, adventure, fantasy, most of the time with a male protagonist, etc. and the latter focuses more on romance, friendship, growing up, most of the time with a female protagnist, yadda yadda).
The comics we know today as "shonen" are just the ones that have defined the genre from being so popular (/cough naruto, bleach, one piece /cough). There are plenty of comics out there that would technically fall under shonen/shoujo/bishoujo, as long as you aren't too selective about what it's SPECIFICALLY like (like Naruto). Those are just the comics that ended up navigating the modern-day shonen ship
So any shonen out there? Yes. Any cookie-cutter Naruto comics out there? Not as many, but I'm sure you'll find some if you dig deep enough 