None of them, for me. I like the Switch and I would like it more if I bought a few more games for it, but as things stand I buy any multi-platform titles on the PS4 if I can. Compared to other Nintendo systems it still feels lacking to me, except the Virtual Boy of course or the Pokemon Mini or other obscure consoles they have released over the years. This is going to be a subjective opinion based on my personal use and enjoyment of the console though, if I just look at the sheer number of games I could potentially get on Switch, then it's hard to deny that it's at least competing for the best console that Nintendo have ever had.
But as for my personal enjoyment, I like Mario Odyssey, it's on par with 3D World and Sunshine for me. It does have the best iteration of Smash Bros, in my opinion, so that's something. But then I don't care for Splatoon, I already played Mario Kart 8 for hundreds of hours on Wii U so I won't play the Switch version, technically it's probably slightly better on Switch but that does nothing for me. Tropical Freeze is in the same position and so is Captain Toad. The Final Fantasy games would be a huge thing for me, but I already own all those titles elsewhere. I do really want that version of FFXII and if Square won't update the PS4 port then I might end up getting it on Switch, since it is one of my favourite games ever it could really change my opinion of the console. Just thinking of owning a portable version of FFXII is incredibly exciting for me and I always wanted the PSP or Vita to get it. Now the Switch has it and it's hard to resist buying it right now.
Breath of the Wild is falling as time goes on, what was a solid 7/10 game for me at launch is now a 5/10. At this point I might play the first Zelda game over BotW just because it's a shorter game, I rate them about the same though. The Wii U has the ability to play Wind Waker, Twilight Princess, Skyward Sword, Ocarina of Time, Majora's Mask, Minish Cap and A Link to the Past, all of which I vastly prefer. It also has Zelda 1,2, the DS games and even Breath of the Wild, but since I don't own it on Wii U that doesn't really matter. Those Zelda games really give the Wii U a boost in my eyes, it's true that they are all just older games, but unlike Mario Kart or Tropical Freeze, I will play these games over and over on any system. The Wii U is a Zelda machine for me and that alone really makes it stand above the Switch.
I do like Kirby and Yoshi on Switch but they are both no better than previous instalments. The Switch is home to my favourite version of Phantasy Star though, that's pretty good going in my books, in fact the Sega Ages titles have impressed me so far, except for Sonic which was done better on older consoles. The NES games on the online service are nice but most of them are on Wii, Wii U, 3DS and of course the NES, but I'd say it's one of the higher points for the Switch right now.
The Switch does have one big thing going for it in terms of the actual hardware and that is the hybrid nature of the console. That is a really nice concept, it's just a shame that since release I have barely played my Switch. It should be my favourite Nintendo console ever and maybe it will be eventually, but I can't call it that right now.
Metroid Prime 4, Pikmin 4, Luigi's Mansion 3, Link's Awakening and other future games could help the Switch surpass other Nintendo consoles in my eyes, or just get a good port of FFVIII and it'll automatically get promoted to top 5 consoles ever. Well, top 6 really, PS1, PS2, PS3, PSP and Vita already play FFVIII but if the Switch got a slightly enhanced definitive version of the game, then it'd probably just be the best console ever and I'd even buy the limited edition FFVIII Switch model just to cry tears of pure joy at such a magnificent piece of technology.