Tough question to answer, really.
If we're talking in terms of industry-leading, standard-setting games in the technical/visual/fidelity/storytelling sense, as well as select genres like racing sims, the answer is Sony/SIE. Between Ico, Shadow of the Colossus, Uncharted, Killzone 2, TLOU, GT3, GT4 and more, I think they've been the most consistent. Specifically on grounds of technical showcases and pushing gaming forward that way, SEGA is a very close second IMO when you go from Outrun to Virtua Fighter, to Sonic (there was no other platformer looking that good in 1991) to VF3, to Shenmue.
If we're talking in terms of best IP retention regarding quality & selling power, massive brands, and being industry-leading & standard-setting in terms of game design, then the answer is Nintendo. They are hands-down the best as long-term IP retention in the industry, not just 1P-wise but in terms of ANY publisher, period. Brands like Mario and Zelda are bigger than ever and have retained a high standard of quality for decades. Meanwhile, stuff like Pokemon are still massive cultural sensations, and they really helped set the standard for various genres like 2D & 3D platformers, moody/thematic platformers (Super Metroid), kart racers, and more.
If we're talking in terms of sheer variety in 1P offerings, I think in time the answer could be Microsoft, but mainly down to all the studios and publishers they spent over $80 billion acquiring. Which, well, isn't helping their actual consoles a single lick. So in terms of just who I'd pick for now, that answer is SEGA. The sheer number and variety in games SEGA developed & published between their home consoles and arcade systems is legendary, quite a lot of them being very fun games with some being industry-leading and standard-setting in their own right like Sonic, Daytona USA, Virtua Fighter and Shenmue. I don't think SEGA gets enough credit for the influential games they contributed to the industry, even if Nintendo ultimately contributed more in that regard.