Here is a website Nintendo just launched which shows you overall playtime for 3DS & Wii U, as well as your top 3 most played on both systems: https://my-nintendo-3ds-wiiu-memories.nintendo.com/en-US/index.html#top
3348 hours overall
Total titles played is 98
1. ACNL - 325 hours (ACNH blows this out of the water for me)
2. Pokemon Y - 316 hours
3. Pokemon Sun - 305 hours
1800 hours overall
Total titles played is 61
1. Smash Wii U - 385 hours (SSBU blows this out of the water as well)
2. BOTW - 299 hours (Daily Log actually says 300 even)
3. Mario Kart 8 - 220 hours (I have 140 in MK8DX, but I could see DX surpassing it)
Seems like roughly half of my playtime comes from just these three, not surprisingly!
I know it is kind of a pointless feature because 3DS & Wii U do a good job tracking playtime, but this is still nice to have. Would've been a pain to add up the total playtime anyways.
My most played on Switch are ACNH (725 hours), SSBU (545 hours) & MK8DX (140 hours). Fully expect ACNH to reach 1,000 one day and I think SSBU could reach 700. As mentioned, I think MK8DX can surpass MK8. I don't think I have any other titles exceed 100 hours, but I do have a lot in the 70 range. I don't play Pokemon as much as I did.
What are your stats and would you like to share your Switch stats?