It really all depends on whether you're talking about portables, home consoles or the two combined.
If we compare all consoles, no single Nintendo console was able to sell more than all PS consoles, because the PS2 sold 157m lifetime while the DS sold 154m. However, if you combine portables and home consoles for one generation, you would be right since the Wii + DS combo gave 101.63m + 154.02m = 255.65m, while the PS2 + PSP combo gave 157.68m + 80.82m = 238.5m. Still, while Nintendo won that gen, those numbers were awefully close, and Nintendo struck lightning that gen, something they didn't consistently do for every gen. Well, in fairness the same can be said about the playstation, which now has bowed out of the portable space in favor of supporting their main home console line and the PS3 almost fell flat on its face until they picked themselves up. Now that the Switch combines both, let's wait and see what the final numbers are before we celebrate, since Nintendo will be shipping its greatest numbers this year, and apparently that 30m matches the most shipped for the DS in the past according to a post I read in another thread.
Also, Nintendo is stronger in certain markets with its portables, and stronger in others with its home consoles. But when home & portable are combined their presence is fairly equal worldwide. Still, they are strong in sales of certain genres in certain regions, and weaker in other genres and while they absolutely dominate japan now, Sony is definitely the winner in Europe and in America it's shared ground. Also, while the switch combines both home and portable experiences, Nintendo is capable of making good or bad decisions for consoles, so the future is not cemented (Wii +DS was huge while 3DS + WiiU was weak at ~89m total HW sold). The most important for Nintendo is to continue to sell relevant and compelling HW that makes sense, to be careful with their gambles going forward, making sure their risks will bring reward (since now they only have one console and not two lines), and that they make games that bring long-term interest and avoid short-term cash-grabs like the plague. This is paramount for Nintendo to succeed.
They're a great company with a warchest of highly attractive IPs, but as the past has shown, if they don't manage the value of their brands and platforms and squander them with poor decisions in how they market those things, they will get hit hard. And this industry doesn't forgive easily, like it has shown so far in the history of Nintendo. They are a company with immense potential, and their games sell strong always, on that nobody can disagree with you. Come rain or shine Nintendo GAMES sell gang-busters, but they need to be careful with their brand so the potential of their sales is not impacted.