Let's start by taking a quick look at what this "famous" blaster delivers. It's a moderately challenging affair, and it boasts a few interesting tunes. Not exactly the stuff of legends there, but this story only gets worse: dinky weaponry; small, unimpressive enemies; lots of slowdown; and boring space-themed levels make this an outdated, geriatric shooter, a wash-up through and through. Timeless, this is not.
It doesn't matter to me that Gradius was a "landmark" shooter. Whatever was "special" about it back in the day has lost its sheen, leaving behind something decrepit, uninteresting, and deserving of whatever mockery is hurled its way.
That certainly isn't the case with all old shooters. Check out R-Type for a classic that has actually remained respectable over the years; hell, some stretches of R-T still come off as examples of ingenious stage design. Returning to the Konami catalog, both Parodius and Salamander completely murder Grandpa Gradius; and while the game's own direct sequel (which was released as a PCE Super CD) is hardly wonderful itself, it leaves its forerunner in the dust as far as stage concepts and boss designs go. What with the existence of these superior alternatives (and the many others that are out there), this old-timer is hardly even worth playing anymore.