Well... since I haven’t really liked anything retro has ever done... and loved just about everything monolith has done.... it really isn’t even a question to me. In my eyes, retro was never better, nor even that good of a studio...

Yup, I do appreciate their sense of scope, but questionable mechanics distract from that a lot.

Xenoblade so far has some solid foundations, but they just keep adding more and more instead of polishing what is already there I feel.

I'd consider monolyth better IF they can create another hit IP. Retro has two.
Insys still blows both away. They've been there since the beginning, developing hardware, and also being in charge and creating three classic ninty ips: wars, fire emblem, and paper mario.

Why is that even relevant? So the oldest development studio automatically wins?

Retro Studios was formed from former Iguana Entertainment employees, who are best known for the classic Turok series. 

Intelligent Systems is a decent developer with a very high output, but that comes at a cost as they've developed quite a few mediocre and even down right terrible games: 

- Game & Wario (terrible)

- Paper Mario Sticker Star (terrible)

- Paper Mario: Color Splash (mediocre)

- Code Name: S.T.E.A.M. (terrible)

I'll make that call when Retro releases another game. Monolith Soft has released two Xeno games and supported Zelda: BotW in the time since Retro's last game. 2.5 games certainly impress me more than nothing.

If we talk about their individual legacies as a whole, well...I'd probably say Monolith Soft has appealed to me more, but that's also personal preference. The Metroid Prime games are pretty awesome...but Xenoblade Chronicles 1 and 2 have completely absorbed me on a whole nother level.

When a studio only releases a couple of co-developed 2D platformers rated 8.5/10 over the course of 11 years, they're NOT an elite studio. They're a B-tier studio.

This silly joke about Retro studios being the best studio in the world needs to stop. They're Nintendo's second-to-the-bottom studio, only in front of Nd Cube.

Code name steam is great.

Aanyways, the fact is that they've created 3 beloved  ninty IPs fromscratch

 for the paper mario situation... not really thier fault that the director for PM64 and TTYD wanted to do something else. (He's currently busy with the fairly sucessful, if japan only, fire emblem TCG. My point is that they've made for more of an impact in ninty than either rare or monolyth, ESPECIALLY in japan. More so since the prime series actually turned off fans in japan.

Nintendo is a global company, not Japan only. 

Metroid Prime is the best selling Metroid game, so they must have done something right. Donkey Kong Country: Returns is also the best selling non-bundled Donkey Kong Country game. 

Prime is the best selling because people thought it was going to be a Halo like shooter it's only when they purchased it and played it when they realised it was completely different this is why the is a large drop in sales between Prime and Echoes and why Corruption was more shooter like in comparison.

Bollocks, the game was never advertised as a Halo-like shooter. 

There's also a huge drop between Metroid and Super Metroid or Super Mario Galaxy 1 & 2. It doesn't really mean anything.