I don't really have a ranking system so I'll just go with relatively recent ones I've watched and thought did well:
Antony Starr is amazing on the show The Boys so he's probably my favorite actor right now. He was good in Banshee as well.
Matthew Rhys is probably up there as my favorite actor. I really enjoyed him in The Americans and Perry Mason.
J. K. Simmons in Counterpart, a slow burning thriller about an older man who has let life pass him by was another performance I enjoyed.
For actresses:
Lauren Cohan, I'll watch her in anything.
María Gabriela de Faría deserves another lead role in a show. Deadly Class was a ridiculous show and I personally think it's forgettable but I liked her performance.
Naomi Scott is another actress I've liked in everything I have seen her in.
And maybe I'm biased because I really enjoyed the show but I also liked the women in Counterpart - Nazanin Boniadi and Olivia Williams. I liked most of the cast but my favorite 3 would be the ones listed (JK Simmons, Nazanin Boniadi, Olivia Williams)