It never really sat well with me how Contra Hard Corps was apparently designed around a three hit-point system (I think it's the only Contra game to even HAVE hit points), and yet that system was just excised entirely out of the Western releases. Hell, the already-easier Japan release has a button code to give you either more lives or continues (I forget which), and that was ALSO taken out of the Western release. It just sounds like the Western release was made arbitrarily harder with little regard for how balanced this would make the game.
Love the pun, though, and the music's kickass.
The code was for more lives; you didn't need more continues, because the Japanese version has infinite continues. Of course, the Western version has both of those things removed, along with the cut to 1 hit per life.
Yes, if it wasn't for that Japanese-language story (and that Hard Corps HAS a story, and a significant amount of it too for the genre), and the region locking, there'd be no reason for anyone other than crazy masochists to consider the US release... but as is, there isn't really an ideal version. I love the game, but the US version is so insanely hard... I really wish that at least they'd left in the infinite continues!
Despite that though, I like the US version of Hard Corps more than I do Gunstar Heroes; it's a better game. It's my favoriite Contra game too, actually... I'm not much of a Contra fan, and prefer stuff like Metal Slug myself, so that Hard Corps is so different from the other ones is actually a good thing, in my opinion. I also might like The Adventures of Batman & Robin more than Gunstar Heroes too, though that's close... Adventures of Batman & Robin is a really good run&gun (/shmup), but also crazy-hard, and it's repetitive -- the game has great graphics, but each area's background and enemy set repeat beginning to end. Still, great game. I don't know, somehow I don't love Gunstar Heroes as much as a lot of people do (though I did really like the GBA game). It is good though, sure... but I do not agree with the "best run&gun ever" stuff.
As for Vectorman, Mega Turrican, and Earthworm Jim, those are really in between run & guns and platformers... it's some hybrid genre. Usually they get put in with platformers, even though there's certainly a lot of shooting. (Of those though, I love Turrican and Vectorman, but don't particularly care for Earthworm Jim. It's okay, but not great. I'd much rather play Universal Soldier, aka the Genesis version of Turrican 2.) If we are comparing them to the run & guns though, Mega Turrican and Vectorman would place ahead of any of them I think. I really love those games...