If the metric is profit for Nintendo, sure, it's number one.
No console comes close to Switch profit. It's the perfect "work less, profit more" box.

Pure profit? Yeah, probably no contenders.

ROI percentage. Gameboy, probably with no contenders as well.

Actually the PS5 is tracking very close. The next FY Sony forecast ¥600b operating profit. Thats only ¥40b less than the switch made in the year ending March 31st 2021 during peak pandemic year when they sold almost 30m hardware units in a year.

I still think the ps2 is being grossly under-valued. It literally sold more units in 2003 than the Gamecube sold lifetime and almost what the xbox sold lifetime. The Switch (and Switch 2) had competition. The ps2 didn't have competition. And operating profits are not net profits, nor is inflation being factored in.  The ps2 still stands as the highest selling console ever, and sold the most software ever.... the answer (IMO) is clearly ps2.

Which I suppose begs the question - is the console that utterly destroys its competition the more successful one, or is it the console which sells huge numbers despite having competitors that are also selling well?

Yeah the competition you face makes a huge difference; for Switch to dominate the market the way NES, 2600, or PS2 did, would require Playstation to completely implode, which in a world where people's digital library is tied to their chosen ecosystem is far less probable than it was in the past when say Atari or Sega collapsed.

PS4/5 were far stronger and more entrenched opponents than Gamecube, Dreamcast, or the OG Xbox were, not to mention the added indirect competition from mobile and a stronger PC sector, on top of a fucked economy that prevented Switch ever getting as dirt cheap as say DS or PS2 did.

For me, the one that dominates.  

From official numbers we get from Sony and Nintendo, i don't think any previous Nintendo or Sony console have earned as much in profits in total as Switch 1 did, so using that definition, yes, no console in history earned as much profit returns as the Switch 1 did. Sony before the PS5 generation in general always earned little profit from gaming compared to Nintendo.

Just yesterday I was comparing NES, PS1 and Wii numbers on how the market changes in a decade. It's easy to see how the "others" have grown during the years. In the 80's the market was basically the first world, in the 90's after the fall of Eastern bloc it was first and second world, today the third world is coming increasingly important.

The 7th generation was quite insane, when you look at the system sales overall, only PS1, PS2 and Gameboy had sold better than the worst selling system of the big three that generation. Also the next gen drop was equally insane.

Well, early on many people who weren't gamers bought PS2 as a cheap DVD-player, but when we go back to 80's, basically everyone played games. The difference is, that the people who were in their 20's in early 80's, are in their 60's and 70's today. Basically the whole 90's was pushing games for boys and young men and away from the family entertainment it was prior to that.