I'm nowadays a PC-gamer myself owning a hefty computer and I love beautiful games like Witcher 3.
But I still think Nintendo has some of the best games ever made on their consoles. Take a look into Super Mario Galaxy series, how they just work, are nice to navigate and play, how you can play the games over and over again and have fun even years after their release. Sure they don't have the fastest hardware, but what they can do with it is just amazing.
I played through the two Galaxy games, the second one I think twice since you get Luigi after the first run... Maybe 8 months ago I was playing through Resident Evil 4 on the Wii to keep myself from buying the PC version, and when I finished I booted up SMG2 again to show a friend, and I was struck by how terrible it has aged... If I do play it again it'll be on the Dolphin Emulator. (4k 60hz SMG2 actually looks really nice: https://www.youtube.com/watch?v=GO8H5F1tCjg)
On the other hand I have hundreds of games on Steam I need to play but sometimes when I just want some random fun for a while I'll dig out some old SNES games (or launch an emulator). No one denies you can make incredible games on weak hardware, but you can't make certain types of incredible games without powerful hardware. And in any case you can always make some really crappy games.
I can't even seriously take the "but Nintendo does good gameplay and design even if their hardware sucks" rationalization anymore. With the possible exception of Splatoon (haven't played it), the other Wii U titles I have played at a friend's (I don't own the console) have, despite raising my expectations, systematically disappointed me in some major way due precisely to the gameplay, not the graphics: Super Mario 3D World, Star Fox Zero (that one hurt the most), Pikmin 3 (actually not so bad but no replay value), Super Smash Bros, Mario Kart, and maybe a couple others I'm forgetting. The next Zelda game is their last chance for me and every gameplay demo I've seen has set my expectations real low.
In short, the level design. I felt the hints of what annoyed me when I was playing the two Galaxy games, and this video really summed up what I find terribly wrong (as opposed to brilliant) with the design: https://www.youtube.com/watch?v=dBmIkEvEBtA It's lazy design. There are other complaints (even other specific issues with the level design I experienced) but that's the big one, it's so bad I don't want to play it ever again, let alone finish it.
But I still think Nintendo has some of the best games ever made on their consoles. Take a look into Super Mario Galaxy series, how they just work, are nice to navigate and play, how you can play the games over and over again and have fun even years after their release. Sure they don't have the fastest hardware, but what they can do with it is just amazing.