I don't think it should "boil down to what you played back in the day".
Consciously indulging in nostalgia is fine. I do it from time to time.
But I think a lot of people use it as a crutch or an excuse to not look beyond what they know, because, they're comfortable liking what they know...and they just don't really care that much.
I'm not saying you haven't played much of the action/shooting/beat 'em ups on the SNES, but like, I'm always like "hmmmm what do you mean?" when people are like "Well the snes only good for Nintendo and RPGS....gunstar heroes rullzzzz".
I'm like "yeah....ok"
You know?
I can understand your points but, the games systems, tv shows, sports team i grew up getting attatched to "back in the day" are the ones that are ingrained in me and are my favourites and yes a copious amount of nostalgia is involved.
I'm far from being a blinkered sega fanboy though (although i will admit to being one) and like i said my second favourite console of all time is the snes and certainly not for the jrpg's.
It's got a fantastic library of games, i just like the MD equivalents more, i'm not one for dissecting a game apart like some michelin restaurant critic, i'm a simple man and if i like a game, meh, i like it, it's as simple as that.
What's wrong with gunstar heroes lol, it's a fantastic run and gun game that's why peeps mention it, better than contra hard corps, but not as good as alien soldier or mega turrican IMO.
TBH if i did a list here of my top 5 brawlers, run and guns, action/platformers and shooters on the 2 systems i'd really not struggle to pick 5 stand out games on both systems in all the genres i've mentioned, but i still rather the MD equivalents lol.