Yeah this thread has got me planning to check out Slam Dunk and Kinnenom(I probably misspelled that). Been meaning to check out some classic Jump and with what's going on. City hunter and fist of the north star are on the list too
The English theme was already posted but the original Japanese OP to Pokemon is just as ubiquitous.
And speaking of the 'mons, if you've only ever heard the English Digimon theme... While I personally consider the JP/US themes for Pokemon to be more or less even, Saban's Digimon song ain't NOTHING compared to Butter-Fly.
Absolutely beautiful opening which is a change from the usual Saint Seiya formula but captures the tone of the Hades Arc really well. This counts as its the first opening for the Hades Arc which was technically different from the original anime.
MP100, FMA:B, and Soul Eater's first OPs are hands down the absolute best (and Bleach's OP1 song is super amazing, too, even if I find the animation a bit boring), but those have all already been mentioned. :)
Soooo, even tho these aren't quite as visually stunning as the above, here are a couple other fav shonen OPs of mine not yet listed: