Even if Switch sells more than PS2...

[JackHandy]

Well, let's list some of the things they have in common, and then let's list the things they don't have in common.

Common things.

1.) They were both culturally-significant devices.
2.) They both sold over 150 million units.
3.) They are both the highest-selling devices for their respective companies.
4.) They both offer the highest-selling individual games for their respective generations.
5.) They both were relatively unreliable hardware wise (stick-drift and fan issues for Switch, DRE for PS2).

Things they don't have in common.

1.) One is a handheld with a dock and one is a dedicated home console.
2.) One of them had a higher market share (PS2) than the other.
3.) One of them had a lock on third party support (PS2) and the other was inferior for third parties (Switch).
4.) One of them was a massive leap forward in tech (PS2), while the other only offered the power of the generation prior (Switch).
5.) One of them had free online play (PS2), while the other hid it behind a paywall (Switch).
6.) One of them used standard media, the other used (sort of) propriety media.
7.) One had full hardware-based backwards compatibility, the other didn't.

I think when you look at it on paper, the PS2 is more impressive. It sold more units and it did so as a dedicated home console. Its market-share was greater. Its games were more revolutionary, because they were doing things never seen or experienced before. It had full, hardware-based backwards compatibility. It had free online play. It had far more third party exclusives, AND great first party games. And most of all, it did all this in a market place that was infinity smaller.

For me, a harder debate would be between the PS2 and SNES, or NES. Now THAT would be a tough one.