Nintendo's relationship with third party publishers on Switch has been interesting to say the least.
Which publisher other than the big N themselves do you think has done best by the Switch, and please elaborate on why they deserve the title?

Bandai Namco I guess

I think SquareEnix. Multiple HD-2D remakes for the Switch and some exclusives like Triangle Strategy. Some people might counter-claim with Final Fantasy, but there is already an agreement with Sony on that franchise back in 2001. In return, they did release Dragon Quest 11 which is also a great game from a huge franchise.

yeah that's also a good one

Square did nice too, their biggest misstep was releasing Kingdom Hearts as cloud-only, I'm still perplexed they will port Nier and not KH. I would understand KH 3 by the others... 

I will always hope they release a spin off, but it's not coming I guess. Dream drop distance is from 2012 and no rumors of any spin-off ever since

Sega - without the Yakuza creator, the support improved

Capcom - a Monster Hunter machine and old games

Namco - lazy ports and late ports

Square Enix - Dragon quest and Asano productions.

Konami - Momataro and olde games. 

None? Koei?

Platinum with Astral Chain and the assumption Bayo 3 is going to be amazing.

Astral Chain is quite a hidden gem, one of the best games I've played.

How do you define "best support"? Is it the raw number of games, quality of games, popularity of games, or what?

If we don't care about the number of games, I can make an argument for Ubisoft or Microsoft, I think.

My only issue is that Bandai Namco can do so much more than what they’re doing now. Sure they’ve ported some solid/great current Gen games (though I wished Soul Calibur VI was ported), older games, and released some unique smaller titles (even developing Smash Ultimate and New Pokemon Snap), but I would like to see bigger new games from their studios that don’t relate to Nintendo franchises. For example, Capcom was able to develop MHRise after MHW, why can’t BN develop an original Tales of game if Arise is considered tough to port? 

Capcom is solid with their retro content, but lacking in their more recent/newer games. There’s not much possibility of the more recent SF games (like 5 or 6) and only rumors of an original Resident Evil title coming to Switch. The Monster Hunter side, though, is great with Rise/Sunbreak and Stories 2 alongside Generations.

Sega/Atlus are kinda like Capcom, but they’ve released more current Gen games like Shining Resonance, Valkyrie Chronicles 4, 13 Sentinels, and, finally, the recent Persona games outside of 5 Strikers. Of course, Sonic has remained a staple and even Frontiers will come out Switch. No Yakuza games though..

Square Enix is probably the best third party developer on Switch in my opinion. Outside of the various retro FF and DQ ports, they’ve established a great trend on Switch. Octopath Traveler was a sign of things to come for Team Asano with the HD-2D focus, leading to Triangle Strategy, Live A Live, and DQ3 Remake. Bravely Default 2 was a solid game. DQXIS was an incredible game that was worth rebuilding from the ground up to work on Switch. Even Nier Automata is coming soon and looks pretty good for a PS4 game being ported. I guess the only issues are that there weren’t any games from their Western studios or Crystal Dynamics before they left (I.e., Tomb Raider, Hitman, etc.) outside of the GotG cloud game unless I missed something and the missed opportunity of the Kingdom Hearts series coming to Switch. Outside of KH3, the rest of the series could’ve been ported instead of being cloud versions. I think fans would’ve waited patiently a little longer if it meant seeing a physical/digital Kingdom Hearts game on Switch, but I guess they wanted to take advantage of the Sora in Smash hype.

Capcom if only for Monster Hunter Rise. Sunbreak is just awesome!