There are MANY generic systems out there, starting with the granddaddy of them all, GURPS.
Which was derivative of Hero (Ok, and TFT, obviously), and not as good. ;P
Notice, most people prefer to use more tightly-focused genre-specific games.
IDK, in the 90s 'most people' seemed to care mainly about setting. Now 'most people' hate 4e.
Actually, most people are unaware of RPGs.
('Most people...' that's become a trigger, for me, it seems...
... I hadn't realized that. Disappointing.)
Those days are LONG LONG past, though GURPS and BRP and a few others have sort of soldiered on
I actually think there's a distinction between a 'core system' like BRP, that is adapted to create different games one at a time, and a Universal system that can be used for any genre. BRP is the first core system that was actually extracted and published separately, a major milestone, IMHO.
TSR had a core system in D&D, using it for D&D, Metamorphosis Alpha, & Gamma World, but never formalizing it... until 2000 when WotC finally did it for them as d20,
and it dominated the industry. Then, 8 years later, dropped the ball, on a bed of nails, stomped on it (caution, severe foot injury), set it on fire, and threw it into a black hole called the GSL. (Not that I'm bitter or anything). Then realized everyone already had their own copy of the ball and they could do nothing, and sheepisly picked it back up and pretended nothing had happened. (Not that I'm bitter or anything.)
With a core system, your designers don't re-invent the wheel, and the players don't need to learn to ride a bicycle over and over, but they still need you to design the next game for them.
Universal systems are like core systems, 'cept you don't need to wait for the next game in a genre that hasn't been covered yet, you can just play it. Worked out so well financially for Hero that they were bought out by a semi-successful corporate lawyer.
That's always been the thing about hypothetical perfection - how do you make money off it?
I mean, its not a BAD concept, but it really suites best games that tend to mix several fairly similar genre or settings together.
Like, not coincidentally, supers, where you might have have a badass with a shield, a disguise expert, an inventor in armor, and a mage all working together.
I'm still prettymuch sold on the hypothetical 'perfect system' being necessarily universal - otherwise, how could it be perfect it if it did some things better than others, those others would be imperfect.
(Sorry to stray so far off topic, Garthanos).