The Sim Supply is my only actual "Simmer" youtuber I watch. His Rags to Riches series are some of my favorites.
His Bigwallet family stuff is really involved, too, though that often is interwoven with the Rags to Riches series.
Though I do like watching some of the smaller series that other Youtubers have done, like CallMeKevin's ongoing series revolving around Jim Pickens. That one's even had points where the story's gone into the Sims 1, 2, 3, and even has some Castaway Stories and Sims Medieval videos. And I guess it's not very fitting to call this particular one a "smaller series" lol.
Then there's RTGame's fooling around in the Sims 3 and 4, which are also funny.
The Bob Family Household videos are just hilarious.
Though there's also RevScarecrow's Sims 2 series I'm still in the middle of.
There are some others, but those are more standalone videos, rather than series.
