Launching in march sure helps. Im surprised the wii was way ahead of the ps1 and ps2 but couldnt outsell any of them lifetime. Did the wii hit a brick wall?
The Wii peaked in 2009, its third year on the market. Sales really began to tank in 2011 when the stream of new releases dried up and there was basically nothing but Skyward Sword, but it still sold over 10 million units that year. It was selling around 20 million units a year for 4 years while the games were coming, 10 million when the year the games topped coming, and around 5 million the year it was replaced.
Despite the claims that the Wii's sales were front-loaded, it actually peaked later in its life-cycle than previous Nintendo home-consoles and saw more consistent sales as well. The most front-loaded Nintendo console is the N64, which sold like crazy at launch for a while in 1997 before losing its momentum that same year. The Gamecube peaked in its second year. The Wii peaked in year 3 and didn't drop off that much until year 5. It was a full 6 years between the launch of the Wii and the launch of its successor, a full year longer than the previous consoles.
PS1 sales really took off later in its lifespan, specifically after Final Fantasy 7 launched in 1997, though it wasn't selling poorly before then.
PS2 is perhaps the most unusual beast of all because it sold over 50 million units AFTER the PS3 launched.
If memory serves, there were periods where both the PS2 and Wii were outselling their immediate successors. The PS1 also sold a ton after the PS2 had launched.
Playstation has one big advantage in that Sony sells in many markets outside of North America, Japan, and Europe that Nintendo doesn't really ship much of any to. But even without that nothing sells tens of millions well into the following generation the way Sony consoles do.
https://www.statista.com/statistics/227012/lifetime-unit-sales-of-nintendos-home-consoles/ (note. I'm going by January-December in my descriptions above, not the fiscal year like this link does).