Dragon Ball - "A Super Saiyan is a legendary warrior! It's not like any Saiyan can become one so easily!" - Nappa

Like so acording to DB Heroes

Then every saiyan after Goku becomes a super saiyan. Excluding Pan and Bra, but that was GT, it made many mistakes. Honestly, Nappa should be upset, if he hadn't died, he'd have become one too.

And sure, it's easy to bring up the Super super saiyans, and Goten and Trunks, but it's not like they're the only cases. Gohan and Future Trunks got it pretty easily too, and Vegeta did it offscreen.